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DONO 
AMICORVM 


// 

-& 


NEW 


TEXT-BOOK 


OF 


GEOLOGY 


DESIGNED 


FOR  SCHOOLS  AND  ACADEMIES. 


BY 

JAMES  D.  DANA,  Li,.D., 

AUTHOR  OF  "A  MANUAL  OF  GEOLOGY,"  "A  SYSTEM  OF  MINERALOGY,"  OF  REPOST8 

OF  WTLKES'S  EXPLORING  EXPEDITION  ON  GEOLOGY,  ZOOPHYTES,  AND 

CRUSTACEA,  "CORALS  AND  CORAL  ISLANDS,"  ETC. 


JFourtfj  iEtJitton, 

REVISED    AND    ENLARGED. 


WOODCUT8. 

\ 


NEW    YORK    •  I  •    CINCINNATI    •  :  •    CHICAGO 

AMERICAN    BOOK    COMPANY 

FROM  THE  PRESS  OK 
IVISON,  BLAKEMAH  &  COMPANY. 


Entered,  according  to  Act  of  Congress,  in  the  year  1868. 

BY    THEODORE   BLISS   &    CO., 

in  the  Clerk's  Office  of  the  District  Court  of  the  United  States  for  the  EaSten 
District  of  Pennsylvania. 


Entered  according  to  Act  of  Congress,  in  the  year  1874. 

BY   IVISON,    BLAKEMAN,    TAYLOR,   &   CO., 
in  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


Copyright,  1883, 

BY  IVISON,    BLAKEMAN,   TAYLOR, 


PREFACE. 


IN  preparing  this  Text-book  of  Geology,  the  general  plan 
of  my  Manual  has  been  retained.  The  science  is  not  made 
a  dry  account  of  rocks  and  their  fossils,  but  a  history  of  the 
earth's  continents,  seas,  strata,  mountains,  climates,  and  liv- 
ing races ;  and  this  history  is  illustrated,  so  far  as  the  case 
admits,  by  means  of  American  facts,  without,  however,  over- 
looking those  of  other  continents,  and  especially  of  Great 
Britain  and  Europe. 

In  this  FOURTH  EDITION,  fifty  pages  have  been  added  to 
the  size  of  the  work,  in  order  to  render  the  explanations 
simpler  and  more  complete,  and  to  give  also  a  fuller  account 
of  the  kinds  of  life  which  contribute  to  rock-making,  of  the 
geographical  distribution  of  marine  species,  and  of  the  depths 
of  the  seas.  Each  of  these  topics  is  illustrated  by  new  cuts, 
and  the  last  by  a  general  map  showing  the  depth  of  the 
Atlantic  and  Pacific  oceans  by  bathymetric  lines,  based 
mainly  on  that  of  Mr.  H.  N.  Moseley,  of  the  Challenger 
expedition.  The  map  of  the  vicinity  of  Naples  is  from 
Murray's  Handbook. 

135480 


iv  PREFACE. 

No  glossary  of  scientific  terms  is  inserted,  because  the 
volume  is  throughout  a  glossary,  or  a  book  of  explanations 
of  such  terms,  and  it  is  only  necessary  to  refer  to  the  Index 
to  find  where  the  explanations  are  given. 

The  teacher  of  Geology,  and  the  student  who  would  ex- 
tend his  inquiries  beyond  his  study  or  recitation-room,  is 
referred  to  the  Manual  for  fuller  explanations  of  all  points 
that  come  under  discussion  in  the  Text-book,  —  including 
a  more  complete  survey  of  the  rock-formations  of  America 
and  other  parts  of  the  world,  with  many  sections  and  details 
of  local  geology,  —  a  much  more  copious  exhibition  of  the 
ancient  life  of  the  several  epochs  and  periods  and  of  the 
principles  deduced  from  the  succession  of  living  species  on 
the  globe,  —  a  more  thorough  elucidation  of  the  depart- 
ments of  Physiographic  and  Dynamical  Geology,  —  a  chap- 
ter on  the  Mosaic  Cosmogony,  —  a  large  number  of  addi- 
tional illustrations,  with  references  to  authorities  and  per- 
sonal acknowledgments,  besides  a  general  chart  of  the 
world. 

The  Text-book  departs  from  the  Manual  in  introducing 
the  subject  of  Dynamical  Geology  before  that  of  Historical 
Geology.  This  order  has  the  advantage  of  supplying  the 
student  early  in  the  course  with  a  knowledge  of  the  forces 
and  operations  in  nature  by  which  geological  progress  has 
gone  forward.  It  has,  at  the  same  time,  its  disadvantages, 
inasmuch  as  the  facts  abou^  the  earth's  strata  must  be 


PREFACE.  V 

learned  before  the  questions  as  to  methods  of  formation 
can  be  fully  appreciated.  These  difficulties  are  so  great 
as  regards  the  subject  of  mountain-making,  that  the  study 
of  Chapter  VI.,  under  Dynamical  Geology  had  better  be 
deferred  until  that  of  the  Historical  Geology  is  completed. 

NEW  HAVEN,  CONN.,  September  1,  1883. 


TABLE  OF  CONTENTS. 


INTRODUCTION 1 

PART  I.  — Physiographic  Geology. 

1.  General  Characteristics  of  the  Earth's  Features      ......  6 

2.  System  in  the  Earth's  Features 14 

PART  II.  —  Structural  Geology. 

I.  PETROLOGY,  OR  THE  CONSTITUTION  OF  ROCKS 20 

1.  General  Observations  on  their  Constituents 20 

2.  Kinds  of  Rocks 29 

II.  CONDITION,   STRUCTURE,    AND  ARRANGEMENT  OF   ROCK-MASSES  39 

Stratified  Condition .  44 

1.  Structure 44 

2.  Positions  of  Strata 50 

3.  Order  of  Arrangement  of  Strata 58 

PART  III.  —  Dynamical  Geology. 

I.  LIFE 62 

A.  Formative  Effects 62 

1.  Kinds  and  Sources  of  Materials 63 

2.  Geographical  Distribution  of  Marine  Life 70 

3.  Peat  Formations 75 

4.  Coral  Reefs 77 

B.  Protective  and  Destructive  Effects 80 

II.  CHEMICAL  ACTION  OF  THE  AIR  AND  WATERS 82 

III.  THE  ATMOSPHERE 86 

IV.  WATER 90 

1.  Fresh  Waters 90 

2.  The  Ocean „     .     .     ,  106 


vnii  CONTENTS. 

IV.  WATER  (continued). 

3.  Freezing  and  Frozen  Waters,  Glaciers,  Icebergs 115 

4.  Formation  of  Sedimentary  Strata 122 

V.  HEAT .    .  124 

1.  Sources  of  Heat 124 

2.  Effects  of  Heat 128 

1.  Expansion  and  Contraction 128 

2.  Igneous  Action  and  Results 130 

3.  Metamorpliism 145 

4.  Formation  of  Veins 150 

VI.  MOVEMENTS  IN  THE  EARTH'S  CRUST  :   THEIR  CAUSES  AND  CON- 

SEQUENCES       156 

General  Considerations 156 

1.  Evolution  of  the  Earth's  Fundamental  Features 163 

2.  Formation  of  Mountain  Chains   .     .     „ 165 


REVIEW  OF  THE  ANIMAL  AND  VEGETABLE  KINGDOMS. 

Distinctions  between  an  Animal  and  a  Plant          173 

1.  Animal  Kingdom 174 

2.  Vegetable  Kingdom 186 

PART  IV.  —  Historical  Geology. 

General  Observations 190 

I.  ARCH.EAN  TIME 199 

II.  PALEOZOIC  TIME 204 

I.  AGE  OF  INVERTEBRATES,  OR  SILURIAN  AGE    ......  205 

1.  Primordial  Period 206 

2.  Canadian  and  Trenton  Periods 210 

3.  Upper  Silurian  Era 219 

II.  AGE  OF  FISHES,  OR  DEVONIAN  AGE 229 

III.  CARBONIFEROUS  AGE,  OR  AGE  OF  COAL  PLANTS 240 

GENERAL  OBSERVATIONS  ON  THE  PALEOZOIC 266 

DISTURBANCES  CLOSING  PALEOZOIC  TIME 276 

III.  MESOZOIC  TIME 283 

REPTILIAN  AGE 284 

1.  Triassic  and  Jurassic  Periods 285 

2.  Cretaceous  Period 310 

GENERAL  OBSERVATIONS  ON  THE  MESOZOIC 324 


CONTENTS.  ix 

IV.  CENOZOIC  TIME 329 

I.  TERTIARY  AGE,  OR  AGE  OF  MAMMALS 330 

II.  QUATERNARY  AGE,  OR  ERA  OF  MAN 347 

1.  Glacial  Period 348 

2.  Chainplain  Period 355 

3.  Recent  Period .    .  359 

III.  LIFE  OF  THE  QUATERNARY „    .    .  362 

IV.  GENERAL  OBSERVATIONS  ON  CENOZOIC  TIME 373 

V.  GENERAL   OBSERVATIONS   ON   GEOLOGICAL   HISTORY  .  375 

VI.  CONCLUDING    REMARKS                                                           ,  394 


APPENDIX. 

A.  Map  of  the  Vicinity  of  Naples 398 

B.  Catalogue  of  American  Localities  of  Fossils 399 

C.  Geological  Implements,  etc 403 

D.  Catalogue  of  Minerals  and  Rocks  for  Instruction     .     , 405 

INDEX  ,    .    ,     c    .„.„.....  407 


INTRODUCTION. 


The  Science  of  Geology.  —  Beneath  the  soil  and  waters  of 
the  earth's  surface  there  is  everywhere  a  basement  of  rocks. 
The  rocky  bluffs  forming  the  sides  of  many  valleys,  the  ledges 
about  the  tops  of  hills  and  mountains,  and  the  cliffs  along 
sea-shores,  are  portions  of  this  basement  exposed  to  view. 
Geology  is  the  science  that  studies  these  rocks,  not  merely 
to  learn  about  ore-beds,  coal,  and  building  materials,  but  pri- 
marily to  gather  from  them  facts  about  the  earth's  history,  — 
the  history  of  its  rocks,  features,  and  life.  It  is  an  outdoor 
science,  and'  out  of  doors  are  found  the  best  instruction-places 
for  pupils  and  teacher. 

In  most  of  the  rocky  bluffs  over  the  country  the  rocks  lie 
in  successive  beds.  The  beds  differ  in  thickness  and  in  other 
ways.  They  may  be  all  sandstone,  and  show  the  grains  of 
sand  distinctly  under  a  pocket-lens.  One  or  more  of  the  beds 
may  contain  pebbles,  smoothly  worn  pebbles  with  sand,  the 
material  of  a  gravel  bed ;  another  may  be  a  slaty  layer,  so  soft 
and  fine-grained  that  if  ground  up  and  mixed  with  water  it 
will  make  mud,  —  suggesting  that  it  might  have  been  formed 
out  of  mud.  Should  it  be  inferred,  after  examining  such  a 
bluff,  that  the  beds  were  once  real  sand-beds,  gravel-beds, 
mud-beds,  which  in  some  way  were  spread  out  in  succession, 
and  finally  became  hardened,  it  would  be  a  right  geological 
conclusion. 

1 


2  INTRODUCTION. 

But  the  questions  would  arise :  How  were  the  pebbles 
rounded  ?  How  were  the  mud,  sand,  and  gravel  distributed 
in  beds  ?  Whence  the  sand,  pebbles,  and  mud  ?  At  the  foot 
of  such  a  bluff  there  commonly  lie  heaps  of  loose  sand  and 
stones  derived  from  the  bluff.  The  rains,  frost,  and  other 
causes  keep  wearing  its  surface,  dropping  grains  and  tumbling 
down  fragments;  and  thus  the  heaps  of  debris  are  formed. 
If  a  stream  runs  by  the  base  of  such  a  bluff,  the  water  when 
in  rapid  flow  will  wear  it  and  carry  off  the  material,  grinding 
and  rounding  the  fallen  fragments.  If  the  bluff  stands  on  a 
seashore,  the  waves  will  beat  against  its  exposed  front,  and 
aid  other  destroying  agencies  in  the  work  of  reducing  it  to 
sand,  stones,  and  mud  for  distribution  off  the  shore  and  up 
the  beach. 

All  over  the  world  the  exposed  rocks  of  hills,  mountains, 
and  plains  are  undergoing  wear  and  decay,  and  becoming 
reduced  to  earth  and  coarser  loose  material.  And  if  the 
whole  world  is  thus  engaged,  and  has  always  been  at  this 
work  since  rocks  were  first  exposed  to  the  action  of  the  air 
and  waters,  there  ought  to  have  been  at  all  times  material 
enough  for  the  soil  and  the  rocky  beds  of  all  periods  in  the 
history. 

Along  the  sides  of  a  river- valley  may  often  be  seen  beds 
of  unsolidified  sands  and  gravel,  with  sometimes  clay,  consti- 
tuting low  bluffs.  These  bluffs  may  be  similar  in  the  material 
of  the  beds  to  the  rocky  bluff  alluded  to,  and  the  absence  of 
consolidation  may  be  the  chief  difference.  Up  or  down  the 
valley  evidence  may  usually  be  found  that  such  beds  of  loose 
material  are  much  like  deposits  now  made  by  the  stream  at 
high  flood-level ;  that  the  waters  where  rapid  are  always  mak- 
ing and  rounding  pebbles,  and  in  flood-times  are  carrying 
down  stream  the  ground-up  material  for  deposition  below. 
If  such  beds  of  gravel  and  sand  are  at  too  high  levels  to  be 
made  by  modern  floods,  they  are  sure  to  be  within  the  range 
of  some  greater  flood  of  past  geological  time.  Along  a  sea- 


INTRODUCTION.  3 

shore  there  are  often  similar  bluffs  which  the  sea  has  made ; 
and  great  sand-flats  off  the  coast,  formed  from  sand  and  peb- 
bles drifted  by  the  sea-currents  and  waves ;  and  rivers  carry 
to  the  ocean  a  great  amount  of  sediment  to  add  to  the  marine 
deposits.  The  inference  from  the  facts  that  the  hard  rocks 
are  only  consolidated  deposits,  and  that  they  were  spread  out 
in  beds  in  the  same  ways  that  beds  are  now  formed  along 
or  off  seashores,  in  river  valleys,  and  about  lakes,  is  right 
according  to  the  fullest  evidence  from  geological  investiga- 
tion. Nine  tenths  of  the  rocks  studied  by  the  geologist  are 
water-made  rocks,  and  nearly  all  the  older  water-made  kinds 
are  of  marine  origin. 

Eocky  bluffs  often  consist  in  part  or  wholly  of  beds  of 
limestone.  At  the  Bermudas,  about  Florida,  and  in  other 
warm  seas,  the  process  of  making  limestones  out  of  shells 
and  corals  can  be  studied;  for  the  process  is  now  going  on 
as  in  ancient  time. 

The  beds  of  a  bluff  may  contain  shells,  corals,  bones,  or 
plant-remains,  —  fossils,  as  they  are  called,  from  the  Latin 
word  fossilis,  signifying  dug  up.  Such  a  discovery  opens  up 
a  new  subject.  The  shells  or  bones  could  not  have  got  there 
except  when  the  layer  containing  them  was  forming.  They 
are  like  the  shells  in  the  mud  or  sand  of  existing  sea-bottoms 
or  sand-beaches.  If  they  turn  out  to  be  marine  fossils,  the 
bed  is  of  marine  origin.  But  another  lesson  is  taught;  for 
the  fossils  make  known  what  species  were  living  in  the  seas 
when  the  bed  was  made.  In  a  bed  higher  up  in  the  series 
the  fossils  may  be  different  in  kind,  showing  that  when  that 
bed  was  in  progress  the  old  species  had  gone  and  new  kinds 
had  corne  in.  In  this  way  geology  has  learned  much  with 
regard  to  the  life  that  existed  on  the  globe  wThen  each  of 
the  successive  rocks  was  made.  Taking  the  whole  geological 
series  of  rocks  together  from  the  bottom  to  the  top,  —  the 
maximum  thickness  of  which  is  over  twenty-five  miles, — 
it  is  found  that  new  kinds  continue  to  appear,  and  the  old 


4  INTRODUCTION. 

to  disappear,  on  passing  up  from  one  level  to  another.  Thus 
a  history  of  the  life  of  the  globe,  from  the  simplest  forms 
of  the  early  rocks  to  mammals  and  man,  has  been  to  some 
extent  made  out. 

From  the  above  explanations  it  is  obvious  that  several 
great  subjects  are  treated  under  Geology.  One  is  the  struc- 
ture of  the  globe,  or  the  arrangement  and  characteristics  of 
the  rocks.  A  second  is  the  historical  succession  in  the  for- 
mation of  the  rocks.  A  third  is  the  historical  succession  in 
the  life  of  the  globe.  A  fourth  is  the  origin  of  the  beds  of 
rock  in  the  earth's  structure ;  for  the  rocks  that  were  made 
in  the  deep  ocean,  or  in  shallow  oceans,  or  along  sea-beaches, 
or  in  lakes,  or  in  river-valleys,  and  so  on,  will  bear  some 
peculiarities  in  structure  or  fossils  that  will  betray  their 
origin. 

Further,  rocks  over  large  areas  have  often  been  raised  or 
pushed  out  of  their  original  positions  and  made  into  moun- 
tains ;  and  the  times  of  these  disturbances  and  the  origin  of 
the  mountains  are  other  subjects  for  geological  study.  And 
such  upturned  rocks  have  sometimes  become  crystallized,  or 
converted  into  marble,  granite,  mica  schist,  and  the  like ;  and 
this  is  another  of  its  topics. 

Over  the  earth's  surface  the  valleys  and  deep  canons  have 
been  made  by  rivers  and  their  tributaries.  And  this  work  of 
the  waters  is  one  part  of  that  of  rock-making;  for  here  the 
waters  have  derived  much  of  their  material.  Water  has 
worked  also  in  the  state  of  glaciers  and  icebergs. 

Again,  in  many  regions  the  earth's  crust  has  been  deeply 
fractured.  Sometimes  mineral  veins  have  formed  in  the  fis- 
sures. Often  melted  rock,  from  unknown  depths,  has  come 
to  the  surface  and  spread  widely  over  it,  thus  adding  fire- 
made  or  igneous  rocks  to  the  water-made.  Occasionally 
volcanoes  have  formed  over  the  larger  fissures ;  and  in  a  few 
places  geyser-regions,  like  that  of  the  Yellowstone  Park,  have 
been  left  as  the  later  work  of  the  lingering  fires. 


INTRODUCTION.  5 

The  above  are  the  more  prominent  subjects  in  Geology. 

Forces  of  past  and  present  time  the  same.  —  The  preceding 
review  teaches  that  the  physical  forces  now  in  action  have 
been  the  same,  and  under  the  same  laws,  through  all  past 
time.  Whether  those  of  the  waters,  the  winds,  heat,  cohe- 
sion, or  of  whatever  kind,  they  have  produced  results  through 
the  ages  like  those  observed  about  us,  with  little  difference 
except  from  greater  intensity  of  action  in  early  geological 
time.  To  existing  nature,  therefore,  we  safely  go  for  the 
means  of  interpreting  the  geological  records. 

Subdivisions  of  the  Science.  —  The  four  principal  branches 
of  the  science  are  — 

1.  Physiographic  Geology,  —  treating  of  the  earth's  physical 
features ;  that  is,  of  the  system  in  the  exterior  features  of  the 
earth.     This  department  properly  includes,  also,  the  system  of 
movements  in  the  water  and  atmosphere,  and  the  system  in 
the  earth's  climates,  and  in  the  other  physical  agencies  or 
conditions  of  the  sphere. 

2.  Structural  Geology,  —  treating  of  the  rocks  of  the  globe, 
their  kinds,  structure,  arrangement  in  beds,  and  various  con- 
ditions or  modes  of  occurrence. 

3.  Historical  Geology,  —  treating  of  the  successive  events  in 
the  history  of  the  rocks,  and  of  the  continents,  oceans,  moun- 
tains, valleys,  sea-limits,  climates,  and  life. 

4.  Dynamical   Geology,  —  treating   of  the   causes,   or   the 
methods,  by  which   all   the   earth's   changes  were   brought 
about,  including  the  making  of  continents,  of  ocean-basins, 
of  rocks,  of  mountains,  of  valleys,  the  causes  of  all  variations 
in  climate,  and  of  all  changes  in  the  earth's  features,  and  in 
its  living  species  as  far  as  open  to  investigation.     The  word 
dynamical  is  from  the  Greek  8w/a/u9,  power  or  force. 


PART  I. 

PHYSIOGRAPHIC    GEOLOGY. 


UNDER  the  department  of  Physiographic  Geology  only  a 
brief  and  partial  review  is  here  made  of  the  general  features 
of  the  earth's  surface. 

THE    EARTH'S    FEATURES. 
1.  General  Characteristics. 

1.  Size  and  form,  —  The  earth  has  a  circumference  of  about 
25,000  (24,899)  miles.     Its  form  is  that  of  a  sphere  flattened 
at  the  poles,  the  equatorial   diameter   (7,926    miles)   being 
about  26 1  miles  greater  than  the  polar. 

2.  Oceanic   basin  and   continental    plateaus.  —  About    eight 
elevenths  of   the   earth's    surface,  or   144,000,000  of  square 
miles,  are  depressed  below  the  rest,  and  occupied  by  salt 
water.     This  sunken  part  of  the  crust  is  called  the  oceanic 
basin,  and  the  large  areas  of  land  between,  the  continents  or 
continental  plateaus.      The  area  of  the  continents  is  about 
50,000,000    of    square   miles ;    and    that    of    the    islands, 
2,900,000. 

3.  Subdivisions  and  relative  positions  of  the  oceanic  basin  and 
continental  plateaus.  —  Nearly  three  fourths  of  the  area  of  the 
continental  plateaus  are  situated  in  the  northern  hemisphere, 
and  very  nearly  three  fifths  of  the  oceanic  basin  in  the  south- 
ern hemisphere.     The  dry  land,  as  shown  in  the  following 
figure,  may  be  said  to  be  clustered  about  the  North  Pole, 
and  to  stretch  southward  in  two  masses,  an  Oriental,  includ- 


8 


PHYSIOGRAPHIC  GEOLOGY. 


ing  Europe,  Asia,  Africa,  and  Australasia,  and  an  Occidental, 
including  North  and  South  America.  The  ocean  is  gathered 
in  a  similar  manner  about  the  South  Pole,  and  extends  north- 


Fig,  i. 


ward  in  two  broad  areas  separating  the  Occident  and  Orient, 
namely,  the  Atlantic  and  Pacific  Oceans,  and  also  in  a  third, 
the  Indian  Ocean,  separating  the  southern  prolongations  of  the 
Orient,  namely,  Africa  and  Australasia. 

The  Orient  is  made,  by  this  means,  to  have  two  southern 
prolongations,  while  the  Occident,  or  America,  has  but  one. 
This  double  feature  of  the  Orient  accords  with  its  great 
breadth ;  for  it  averages  6,000  miles  from  east  to  west,  which 
is  far  more  than  twice  the  mean  breadth  of  the  Occident 
(2,200  miles).  See  the  following  map. 

The  inequality  of  the  two  continental  masses  has  its  paral- 
lel in  the  inequality  of  the  Pacific  and  Atlantic  Oceans ;  for 
the  former  (6,000  miles  broad)  is  more  than  double  the  aver- 
age breadth  of  the  latter  (2,800  miles).  Thus,  there  is  one 
broad  and  one  narrow  continental  mass,  and  one  broad  and  one 
narrow  oceanic  area. 

The  connection  of  Asia  with  Australia,  through  the  inter- 
vening islands,  is  very  similar  to  that  of  North  America  with 


THE  EARTH'S  FEATURES.  9 

South  America.  The  southern  continent,  in  each  case,  lies 
almost  wholly  to  the  east  of  the  meridians  of  the  northern ; 
and  the  islands  between  are  nearly  in  corresponding  posi- 
tions,—  Florida  in  the  Occident  corresponding  to  Malacca 
in  the  Orient,  Cuba  to  Sumatra,  Porto  Eico  to  Java,  and  the 
more  eastern  Antilles  to  Celebes  and  other  adjoining  islands. 
It  is,  therefore,  plain  that  Australia  bears  the  same  relation 
to  Asia  that  South  America  does  to  North  America.  It  is 
also  true  that  Africa  is  essentially  in  a  similar  position  with 
reference  to  Europe. 

The  northern  portion  of  the  Orient,  or  Europe  and  Asia 
combined,  makes  one  continental  area ;  and  its  general  course 
is  east  and  west.  The  northern  portion  of  the  Occident,  or 
North  America,  is  elongated  from  north  to  south. 

4.  Oceanic  depression  and  Continental  elevations.  —  The  mean 
depth  of  the  oceanic  depression  is  about  12,000  feet;  and  the 
mean  height  of  the  land  nearly  one  twelfth  this  amount,  or 
1,000  feet.     The  greatest  depth  reached  by  soundings  (south 
of  the  Ladrones)  is  27,450  feet ;  the  greatest  height  on  the 
land  (in  Mt.  Everest  of  the  Himalayas)  is  29,000  feet ;  and 
hence  the  interval   between  the  extremes  of  altitude  and 
depression  is  over  ten  miles.     If  as  much  of  the  land  were 
transferred  to  the  oceanic  depression  as  would  bring  both  to 
a  common  level,  the  ocean  would  still  have  a  depth  of  about 
10,000  feet  (Peschel). 

The  mean  height  of  each,  Europe,  Asia,  and  South  America, 
is,  according  to  estimates,  about  1,130  feet;  of  Africa  prob- 
ably not  less  than  1,130  feet ;  of  North  America,  750  feet ; 
of  Australia,  500  feet. 

The  mean  depths  of  the  great  oceans  (as  calculated  by 
Haughton  from  recent  soundings)  are  :  of  the  North  Atlantic 
and  North  Pacific  oceans,  15,000  to  15,500  feet ;  of  the  South 
Atlantic  and  South  Pacific  (and  probably  the  Indian  Ocean) 
about  13,000  feet. 

5.  The  form  of  the  ocean's  bed.  —  The  accompanying  map 
shp<vs  the  general  form  of  the  ocean's  bed  beneath  the  larger 


10  PHYSIOGRAPHIC  GEOLOGY. 

oceans.  From  north  to  south,  along  the  middle  of  the 
Atlantic,  there  is  a  wide  zigzag  ridge  or  plateau,  conforming 
in  trend  to  the  American  coast.  It  lies  at  a  depth  of  6,000 
to  12,000  feet,  while  on  either  side  the  bottom  slopes  away 
to  depths  mostly  between  15,000  and  20,000  feet.  In  the 
small  area  of  4,000  fathoms  and  over,  situated  to  the  north- 
west of  the  island  of  St.  Thomas,  the  United  States  Coast 
Survey  steamer  " Blake"  found,  in  1883,  a  depth  of  27,366 
feet.  This  greatest  depth  and  the  largest  Atlantic  area  of 
deep  water  exist  in  the  western  part  of  the  ocean. 

The  Pacific  also  has  a  central  relatively  shallow  plateau, 
having  the  direction  of  its  longer  axis  between  Fuegia  and 
southeastern  Asia ;  and  its  deepest  portions  are  in  its 
western  half.  One  deep  area  is  east  of  Japan ;  another,  the 
deepest,  south  of  the  Ladrones. 

Thus  in  each  ocean  the  greatest  depths  are  in  the  northern 
hemisphere  and  toward  its  western  border.  Northward  in 
the  northern  hemisphere  the  ocean  shallows  rapidly.  The 
depth  in  Behring's  Straits  is  not  over  150  feet;  and  between 
Great  Britain  and  Iceland  it  does  not  exceed  6,000  feet,  and 
is  mostly  under  600  feet. 

The  ocean's  bottom  has  no  steep  ridges  like  those  of  ordi- 
nary mountain  scenery.  But  broad  elevations  exist  in  some 
parts,  as  found  in  the  soundings  of  the  "  Tuscarora  "  between 
the  Hawaian  Islands  and  Japan.  Besides  these,  there  are 
many  mountain  ranges  rising  abruptly  from  the  depths,  hav- 
ing the  islands  of  the  ocean  as  their  emerged  summits,  which 
rival  in  length  those  of  the  continents.  The  Hawaian  range, 
if  the  coral  islands  in  the  line  of  the  volcanic  islands  are 
included  (see  following  map),  has  a  length  of  2,000  miles ; 
and  it  rises  steeply  from  depths  of  15,000  to  18,000  feet. 
The  mountains  of  Hawaii  have  a  height  above  the  ocean  of 
nearly  14,000  feet;  and  a  depth  of  17,000  feet  was  found 
but  50  miles  south  of  the  island ;  this  making  the  whole 
height  near  31,000  feet.  The  islands  of  the  tropical  Pacific 
make  together  an  island  chain  about  5000  miles  long; 


THE    EARTH'S    FEATURES. 


Fig.  2. 


12 


PHYSIOGRAPHIC  GEOLOGY. 


and  they  are  the  tops   of  a  mountain  chain  of  this  great 
length. 

6.  True  outline  of  the  oceanic  depression.  —  Along  the 
oceanic  borders  the  sea  is  often,  for  a  long  distance  out,  quite 
shallow,  because  the  continental  lands  continue  on  undei 
water  with  a  nearly  level  surface ;  then  comes,  usually  at 


Fig.  3. 

a  depth  of  100  fathoms  or  600  feet,  a  rather  sudden  slope 
to  the  deep  bed  of  the  ocean.  This  is  the  case  off  the  east- 
ern coast  of  the  United  States,  east  and  south  of  New  Eng- 
land. Off  New  Jersey,  as  the  annexed  map  represents,  the 
deep  water  begins  along  a  line  about  80  miles  from  the 
shore ;  off  Virginia  this  line  is  50  to  60  miles  at  sea ;  and 
thus  it  gradually  approaches  the  coast  to  the  southward: 


YHE  EARTH'S  FEATURES.  13 

while  to  the  northward  it  continues  80  to  100  miles  off 
from  the  New  England  coast,  and  passes  far  outside  of 
Nova  Scotia  and  Newfoundland  (see  map,  p.  11).  The 
slope  of  the  bottom,  for  the  80  miles  off  New  Jersey,  is 
only  1  foot  in  700  feet.  The  true  boundary  between  the 
continental  plateau  and  the  oceanic  depression  is  the  com- 
mencement of  the  abrupt  slope.  The  same  abruptness  at 
the  100  fathom  line  exists  in  the  Gulf  of  Mexico,  as  pointed 
out  by  J.  E.  Hilgard.  The  British  Islands  are  situated  on  a 
submerged  portion  of  the  European  continent,  and  are  essen- 
tially a  part  of  that  continent,  the  limit  of  the  oceanic  basin 
—  the  100  fathom  line  —  being  50  to  100  miles  outside  of 
Scotland  and  Ireland,  and  extending  south  around  the  Bay 
of  Biscay.  West  of  the  British  Channel  the  depth  increases, 
in  a  distance  of  only  ten  miles,  from  100  fathoms  to  2,000. 
New  Guinea  is  in  a  similar  way  proved  to  be  a  part  of  Aus- 
tralia. Such  facts  occur  on  most  coasts;  and  they  teach 
that  the  oceanic  depression  is  separated  from  the  continental 
plateaus  by  a  defined  outline. 

7.  Surfaces  of  the  continents.  —  The  surface  of  a  continent 
comprises  (1)  low  lands,  (2)  plateaus  or  talk-lands,  and  (3) 
mountain-ridges.  The  mountain-ridges  may  rise  either  from 
the  low  lands  or  the  plateaus.  The  plateaus  are  great  areas 
of  the  surface  situated  several  hundred  feet,  or  a  thousand 
feet  or  more,  above  the  sea,  or  above  the  general  level  of 
the  low  lands.  They  are  often  parts  of  the  great  moun- 
tain chains.  Sometimes  plateaus  include  a  region  between 
mountain-ridges,  and  sometimes  the  mass  of  the  mountains 
themselves  out  of  which  the  ridges  rise.  For  example,  the 
regions  of  Northern  and  Southern  New  York  are  plateaus 
(the  former  averaging  1,500  feet  in  height,  the  latter  2,000 
feet)  situated  on  the  western  borders  of  the  Appalachian 
chain  ;  and  the  same  is  true  of  the  Cumberland  Table-land  in 
Tennessee.  Between  the  Sierra  Nevada  and  the  Wahsatch 
there  is  a  plateau  of  vast  extent,  having  the  Great  Salt 
Lake  in  its  northeastern  portion ;  its  height  above  the  sea 


14  PHYSIOGEAPHIC  GEOLOGY. 

averages  4,000  feet ;  the  high  ranges  of  the  Humboldt  moun- 
tains rise  out  of  it.  The  eastern  part  of  New  Mexico  is  a 
plateau  of  about  the  same  elevation,  called  the  Llano  Esta- 
cado;  and  Mexico  is  situated  in  another,  from  which  rise 
various  ridges  and  peaks.  The  Desert  of  Gobi,  between  the 
Altai  and  the  Kuen-Lun  range,  is  a  desert  plateau  about 
4,000  feet  high,  while  the  plateau  of  Thibet,  between  the 
Kueri-Lun  range  and  the  Himalayas,  is  11,500  to  13,000  feet 
above  the  sea.  Persia  and  Armenia  constitute  another  pla- 
teau. These  examples  are  sufficient  to  explain  the  use  of 
the  term. 

2.  System  in  the  Earth's  Features. 

L  General  form  of  the  continents  resulting  from  their  reliefs. 

—  The  continents  are  constructed  on  a  common  model,  as 
follows:  they  have  high  borders  and  a  low  centre,  and  are, 
therefore,  basin-shaped.  Thus,  North  America  has  the  Appa- 
lachians on  the  eastern  border,  the  Eocky  chain  on  the  west, 
and  between  these  the  low  Mississippi  basin.  Fig.  4  illus- 

Fig.  4. 


trates  this  form  of  the  continent.  In  the  section,  b  repre- 
sents the  Eocky  Mountain  chain  on  the  west,  with  its 
lines  of  ridges  at  summit ;  a,  the  Washington  chain  (includ- 
ing the  Sierra  Nevada  and  Cascade  range),  near  the  Pacific 
coast ;  c,  the  Mississippi  basin ;  d,  the  Appalachian  chain  on 
the  east. 

South  America,  in  a  similar  manner,  has  the  Andes  on  the 
west,  the  Brazilian  Mountains  on  the  east,  and  other  heights 
along  the  north,  with  the  low  region  of  the  Amazon  and  La 
Plata  making  up  the  larger  part  of  the  great  interior.  Fig.  5 
is  a  transverse  section  from  west  to  east  (W,  E),  showing  the 


THE  EARTH'S  FEATURES.  15 

Andes  at  a,  and  the  Brazilian  Mountains  at  b.  In  these 
sections  the  height  as  compared  with  the  breadth  is  neces- 
sarily much  exaggerated. 

In    the  Orient  there  are  mountains  on  the  Pacific   side, 
others  on  the  Atlantic ;    and,  again,  the  Himalayas,  on  the 

Fig.  5. 

A  A 


south,  face  the  Indian  Ocean,  and  the  Altai  face  the  Arctic  or 
Northern  Seas.  Between  the  Himalayas  (or  rather  the  Kuen- 
Lun  Mountains,  which  are  just  north)  and  the  Altai,  lies  the 
plateau  of  Gobi,  which  is  low  compared  with  the  enclosing 
mountains ;  and  farther  west  there  are  the  low  lands  of  the 
Caspian  and  Aral,  the  Caspian  lying  even  below  the  level  of 
the  ocean.  The  Urals  divide  the  6,000  miles  of  breadth  into 
two  parts,  and  so  give  Europe  some  title  to  its  designation 
as  a  separate  continent.  West  of  their  meridian  there  are 
again  extensive  low  lands  over  Middle  and  Southern  Euro- 
pean Eussia. 

In  Africa  there  are  mountains  on  the  eastern  border,  and 
on  the  western  border  south  of  the  coast  of  Guinea ;  there 
are  also  the  Atlas  Mountains  along  the  Mediterranean,  and 
the  Kong  Mountains  along  the  Guinea  ooast ;  and  the  inte- 
rior is  relatively  low,  although  mostly  1,000  to  2,000  feet  in 
elevation. 

In  Australia,  also,  there  are  high  lands  on  the  eastern  and 
western  borders,  and  the  interior  is  low. 

All  the  continents  are,  therefore,  constructed  on  the  basin- 
like  model. 

2,  Relation  between  the  heights  of  the  borders  and  the  extent 
of  the  adjoining  ocean.  —  There  is  a  second  great  truth  with 
regard  to  the  continental  reliefs;  namely,  that  the  highest 
border  faces  the  largest  ocean. 


16  PHYSIOGRAPHIC  GEOLOGY. 

Each  of  the  continents  sustains  the  truth  announced. 
North  America  has  its  great  mountains,  the  Rocky  chain,  on 
the  side  of  the  great  ocean,  the  Pacific ;  and  its  small  moun- 
tains, the  Appalachian,  on  the  side  of  the  small  ocean.  So, 
South  America  has  its  highest  border  on  the  west ;  and  the 
Andes  as  much  exceed  in  elevation  and  abruptness  the  Rocky 
chain  as  the  South  Pacific  exceeds  in  capacity  the  North 
Pacific.  The  Orient  has  high  ranges  of  mountains  on  the 
east,  or  the  Pacific  side,  and  lower,  as  those  of  Norway  and 
other  parts  of  Europe,  on  the  west ;  and  the  Himalayas,  the 
highest  of  the  globe,  face  the  great  Indian  Ocean  (besides 
being  most  elevated  eastward  toward  the  great  Pacific),  while 
the  smaller  Altai  face  the  small  Northern  Ocean.  In  Africa 
the  eastern  mountains,  or  those  on  the  side  of  the  Indian 
Ocean,  are  higher  than  those  on  that  of  the  Atlantic.  In 
Australia  the  highest  border  is  on  the  Pacific  side ;  for  the 
South  Pacific,  taking  into  view  its  range  in  front  of  East 
Australia,  is  greater  than  the  Indian  Ocean  fronting  West 
Australia. 

Hence  the  basin-like  shape  before  illustrated  is  that  of  a 
basin  with  one  border  much  higher  than  the  other ;  and  with 
the  highest  border  on  the  side  adjoining  the  largest  ocean. 

3,  System  in  the  earth's  feature-lines.  —  The  great  masses  of 
land  and  the  larger  peninsulas  have  in  general  a  triangular 
outline,  pointed  southward.  North  and  South  America  are 
prominent  examples  under  the  principle ;  Africa  is  another, 
and  India  and  the  peninsula  of  Greenland  are  others.  This 
form  is  connected  with  the  general  fact  that  the  directions 
of  coast  lines,  mountain-ranges,  and  the  ranges  of  islands  in 
the  ocean  conform  approximately  to  two  systems  rf  trends, 
one  northeastward  and  the  other  northwestward. 

North  America  derives  its  triangular  outline  (see  map, 
p.  11)  from  the  northeastward  trend  of  the  eastern  coast  and 
the  northwestward  of  the  western  ;  and  these  trends  are 
repeated  in  the  mountain-ranges  of  the  continent,  the  oldest 
and  those  of  most  recent  origin.  In  South  America  the  north 


THE  EARTH'S  FEATURES.  17 

coast  has  the  northwestern  direction,  and  the  east  coast,  the 
northeastern,  and  at  the  east  cape  the  lines  consequently 
make  nearly  a  right  angle.  The  northeastward  trend  char- 
acterizes the  west  coast  of  Europe  and  northern  Africa, 
Scandinavia,  and  the  mountains  of  Norway.  Consequently 
the  trough  of  the  Atlantic  and  its  zig-zag  bottom  "ridge" 
trend  like  the  American  coast.  On  the  contrary,  the  trend 
of  the  Pacific  ocean  is  parallel  nearly  with  the  west  coast  of 
North  America,  and  is  northwestward,  like  that  of  its  central 
underwater  plateau ;  and  the  course  is  at  right  angles  to  that 
of  the  north  Atlantic.  The 
islands  of  the  Pacific  are, 
as  stated  on  page  10, 
grouped  in  long  lines,  or 
ranges,  and  nearly  all  these 
lines  have  a  general  paral- 
lelism to  the  longer  axis 
of  the  ocean.  One  ex- 
ample, that  of  the  Hawa- 
ian  or  Sandwich  Islands, 
is  shown  in  Fig.  6.  But 

„_         _      _        ,  .  H,  Hawaii ;  M,  Maui  ;  0,  Oalm  ;  K,  Kauai. 

New  Zealand  has  the  trans- 
verse   or   northeastward    trend,   and    this    is    continued    in 
islands  both  to  the  north  and  south. 

The  two  courses  here  pointed  out  vary  toward  north  and 
south  on  one  side,  and  east  and  west  on  the  other,  as  shown 
in  the  ranges  of  islands  northeast  and  north  of  Australia. 

O 

There  are  exceptions  to  the  principle  stated ;  but  these 
would  necessarily  have  come  from  the  many  diverse  condi- 
tions on  which  the  making  of  the  earth's  ranges  of  moun- 
tains and  the  outlining  of  its  lands  have  depended. 

The  features  described  have  a  vast  influence  in  adapting 
the  continents  for  man. 

America  stands  with  its  highest  border  in  the  far  west,  and 
with  all  its  great  plains  and  great  rivers  inclined  toward  the 

2 


18  PHYSIOGRAPHIC   GEOLOGY. 

Atlantic ;  for,  through  the  Gulf  of  Mexico,  the  whole  interior, 
as  well  as  the  eastern  border,  has  its  natural  outlet  eastward. 
Had  the  high  mountains  of  the  continent  been  placed  on  its 
eastern  side,  they  would  have  condensed  the  moisture  of  the 
winds  before  they  had  traversed  the  land,  and  sent  it  back,  in 
hurrying  and  almost  useless  torrents,  to  the  ocean ;  but,  being 
on  the  western,  all  the  slopes,  from  the  Atlantic  to  the  tops 
of  the  Eocky  Mountains,  lie  open  to  the  moist  winds,  and 
fields  and  rivers  show  the  good  they  thus  receive. 

Again,  the  Orient,  instead  of  rising  into  Himalayas  on  the 
Atlantic  border,  has  its  great  heights  in  the  remote  east,  and 
its  vast  plains,  even  those  of  Central  Asia,  have  their  natural 
outlet  westvjard,  or  toward  the  same  Atlantic  Ocean.  Thus, 
as  Professor  Guyot  has  said,  the  vast  regions  of  the  world 
which  are  best  fitted  by  climate  and  productions  for  man  are 
combined  into  one  great  arena  for  the  progress  of  civiliza- 
tion. Both  the  Orient  and  the  Occident  pour  their  streams 
and  bear  a  large  part  of  their  commerce  into  a  common 
ocean ;  and  this  ocean,  the  Atlantic,  is  but  a  narrow  ferriage 
between  them,  and  vastly  better  for  the  union  of  nations 
than  connection  by  as  much  dry  land :  3,000  miles  of  dry 
land  would  be,  even  in  the  present  age,  a  serious  obstacle 
to  intercourse;  while  3,000  miles  of  ocean  draw^  the  east!  • 
and  west  only  into  closer  political,  commercial,  and  social 
relations. 

I        ; 


PART  II. 

STRUCTURAL,  GEOLOGY. 


THE  term  rock,  in  geology,  is  applied  to  all  natural  forma- 
tions of  rock-material,  whether  solid,  like  sandstones  and 
slates,  or  loose  sand  and  gravel.  All  sandstones  were  once 
beds  of  loose  sand ;  and  there  is  every  shade  of  gradation, 
from  the  hardest  sandstone  to  the  softest  sand-bed ;  so  that 
it  is  impossible  to  draw  a  line  between  the  consolidated  and 
unconsolidated.  Geology  does  not  attempt  to  draw  the  line, 
regarding  consolidation  as  an  accident  in  the  history  of  the 
earth's  beds  or  deposits  :  an  accident  that  probably  happened 
to  not  a  thousandth  part  of  the  sand-beds  and  mud-beds  that 
have  existed ;  and  yet,  to  enough  of  them  in  each  period  for 
the  preservation  of  the  wonderfully  varied  records  that  are 
the  materials  of  geological  science. 

Eocks  may  be  studied  simply  as  rocks,  —  that  is,  with 
reference  to  their  composition,  —  and  collections  may  be 
made  containing  specimens  of  their  various  kinds.  Again, 
they  may  be  studied  as  rock-masses  spread  out  over  the 
earth  and  forming  the  earth's  crust ;  and,  with  this  in  view, 
the  condition,  structure,  and  arrangement  of  the  great  rock- 
masses,  sometimes  called  terrancs,  would  come  up  for 
consideration.  The  two  subjects  under  Structural  Geology 
are,  therefore :  1.  Petrology,  or  the  Constitution  of  Eocks ; 
2.  The  Condition,  Structure,  and  Arrangement  of  Rock-masses 
or  Terranes. 


20 


STRUCTURAL   GEOLOGY. 


I.— PETROLOGY. 
1.  General  Observations. 

Rocks  consist  essentially  of  minerals,  and  the  minerals  of 
the  common  rocks  are  of  four  groups  :  — 

1.  QUARTZ,  called  in  chemistry,  silica  and  silicon  dioxide. 

2.  SILICATES,  or  compounds  of  silicon  in  the  dioxide  state 
with  other  substances. 

3.  CARBON,  the  chief  element  of  charcoal  and  mineral  coal, 
and  a  constituent  of  carbonic  acid  or  carbon  dioxide. 

4.  CARBONATES,  or  compounds  of  carbon  in  the  dioxide 
state  with  other  substances. 

1.  QUARTZ,  OR  SILICA.  —  Quartz  far  exceeds  all  other 
species  in  abundance.  It  consists  of  one  atom  of  silicon 
and  two  of  oxygen,  its  formula  being  Si  O2.  It  is  one  of  the 
hardest  of  common  minerals ;  does  not  melt  before  the  blow- 
pipe, and  does  not  dissolve  in  water,  or  in  the  ordinary  acids. 
Its  hardness  and  durability  especially  fit  it  for  this  place  of 
first  importance  in  the  material  of  the  earth's  foundations. 

It  is  often  seen  in  crystals  like  Figs.  7,  8,  though  generally 
occurring  in  massive  forms,  or  in  grains  or  pebbles.  It  is 
distinguished  ordinarily  by  its  glassy 
aspect,  whitish  or  grayish  color,  and  an 
absence  of  all  tendency  to  break  with 
a  bright  even  surface  of  fracture  (a 
quality  of  crystals  called  cleavage). 
Although  usually  nearly  colorless  or 
white,  it  is  often  reddish,  yellowish, 
brownish  (especially  smoky  brown), 

and  even  black;  and  the  lustre  is  sometimes  very  dull,  as 
in  chalcedony,  flint,  and  jasper.  The  sands  and  pebbles  of 
the  sea-shores  and  gravel-beds  are  mostly  quartz,  —  because 
quartz  resists  the  wearing  action  of  waters  better  than  any 


Fig.  7.          Fig.  8. 


CONSTITUTION   OF  EOCKS.  21 

other  common  mineral.  For  the  same  reason,  most  sand- 
stones and  conglomerates  consist  mainly  of  quartz, 
i-  The  hardness  (on  account  of  which  it  scratches  glass 
easily),  infusibility,  insolubility,  non-action  of  acids,  and 
absence  of  cleavage  are  the  characters  that  serve  to  distin- 
guish quartz  from  the  other  ingredients  of  rocks. 

But  while  quartz  is  so  refractory,  it  easily  fuses  when 
mixed  and  heated  with  potash,  soda,  lime,  or  an  oxide  of 
iron,  into  glass.  Ordinary  glass  is  made  by  mixing  powdered 
quartz  with  soda  or  potash  and  sometimes  lime,  and  subject- 
ing the  mixture  to  a  high  heat.  Sodium  carbonate  is  hence 
conveniently  used  in  blow-pipe  experiments  for  distinguish- 
ing quartz. 

Although  quartz  is  one  of  the  original  minerals  of  the 
earth's  crust,  and  has  been  mostly  derived  from  the  earlier 
rocks  of  the  globe,  part  of  it  has  passed  through  living  beings, 
either  plants  or  animals  and  is  of  organic  origin ;  for  some  of 
the  lowest  species  of  these  kingdoms  of  life  have  the  power 
of  making,  by  secretion,  siliceous  shells  or  siliceous  particles 
or  spicules  in  their  texture ;  and  beds  of  limited  extent  have 
been  made  of  these  microscopic  siliceous  shells  and  spicules. 
(See  page  67). 

2.  SILICATES. — Many  of  the  common  rock-making  minerals 
are  silicates,  or  combinations  of  silicon  with  certain  basic 
elements  and  oxygen;  that  is  with  the  constituents  of  the 
bases  alumina,  magnesia,  lime,  potash,  soda,  oxides  of  iron,  and 
a  few  others. 

Pure  alumina  is  the  most  important  of  the  above-men- 
tioned bases.  It  consists  of  aluminum  and  oxygen  (A12  03). 
It  is  very  hard,  infusible,  and  insoluble,  and  therefore  adapted 
to  its  place  as  second  in  abundance  to  silica.  When  crys- 
tallized, it  is  the  hardest  of  all  known  substances,  except- 
ing the  diamond,  it  being  the  gem  sapphire,  and  the  essen- 
tial ingredient  of  emery.  The  species  is  called  corundum  in 
mineralogy. 

Magnesia  (magnesium   and   oxygen,  Mg  0),  well   known 


22  STRUCTURAL  GEOLOGY. 

under  the  form  of  calcined  magnesia,  is  as  hard  as  quartz 
when  crystallized,  and  equally  infusible  and  insoluble. 

Lime  (calcium  and  oxygen,  Ca  0)  is  common  quick-lime,  the 
calx  of  the  Eomans,  whence  the  term  calcium  for  the  metal. 

Potash  (potassium  and  oxygen,  K2  0)  and  soda  (sodium  and 
oxygen,  Na2  0)  are  the  alkalies  ordinarily  so  called. 

Iron  protoxide  (Fe  0)  and  Iron  sesquioxide  (Fe2  03)  are  the 
two  oxides  of  iron  whose  constituents  exist,  like  those  of  the 
above  bases,  in  many  silicates. 

The  silicates  which  contain  only  the  constituents  of  alu- 
mina are  infusible,  as  well  as  very  hard.  But  those  which 
contain  the  elements  of  either  of  the  other  bases  mentioned 
are  with  few  exceptions  fusible,  and  therefore  fit  to  be  the 
ingredients  of  igneous  or  volcanic  rocks. 

The  following  are  the  most  common  of  these  silicates :  — 

1.  Feldspar.  —  The    feldspars    are   silicates,  containing  the 
constituents  of  alumina,  a  sesquioxide,  along  with  those  of 
the  protoxide  bases,  potash,  soda,  or  lime.      They  are  hard 
enough  to  scratch  glass,  but  less  hard  than  quartz.     They 
break  easily,  or  have  cleavage,  in  two  directions,  with  flat  lus- 
trous surfaces ;  and  the  two  cleavage-surfaces  meet  nearly  or 
quite  at  a  right  angle.    The  color  is  usually  white  or  flesh-red, 
and  rarely  dark  brown  or  greenish.     The  specific  gravity  is 
2.4—2.7. 

The  most  common  kind  is  a  potash  feldspar,  and  is  called 
orthoclase;  another,  named  albite,  is  a  sw&x-feldspar ;  two 
others,  oligoclase  and  labradorite  are  soda-lime  feldspars. 

2.  Mica.  —  Mica  is  a  silicate  containing  the  constituents  of 
alumina,  along  with  those  of  potash  and  lime,  like  the  feld- 
spars, but  also  those  of  magnesia  and  oxide  of  iron.     Mica 
cleaves  easily  into  tough  leaves,  thinner  than  the  thinnest 
paper,  which  are  somewhat  elastic.     It  fuses  with  great  diffi- 
culty.    Its  most  common  colors  are  whitish,  brownish,  and 
black.     On  account  of  its  easy  cleavage,  transparency,  and 
difficult  fusibility,  it  is  often  used   in  the  doors  of  stoves. 
The  most  common  kind  of   mica    has  a  light  color  and  is 


CONSTITUTION  OF  KOCKS.  23 

called  muscovite;  another,  usually  black  in  color  (because  of 
the  amount  of  iron  present),  is  called  biotite.  Some  micas 
contain  water,  that  is,  are  hydrous ;  and  these  hydro-micas,  as 
they  are  called,  are  pearly  in  lustre,  feel  a  little  soapy,  and 
are  sometimes  mistaken  for  talc. 

The  minerals,  quartz,  feldspar,  and  mica  are  the  constituents 
of  granite ;  and  they  may  be  distinguished  in  it  as  follows : 
the  grains  of  quartz,  by  their  more  glassy  lustre,  grayer 
color,  and  want  of  cleavage ;  the  grains  of  feldspar,  by  their 
cleavage ;  the  grains  of  mica,  by  their  very  easy  cleavage  by 
means  of  the  point  of  a  knife-blade  into  thin  elastic  leaves. 

3.  Chlorite.  —  Resembles  black  mica  in  constitution,  and, 
when  well  crystallized,  in  its  cleavage  ;  but  it  contains  14  per 
cent  of  water  and  no  potash.     Moreover  its  leaves  are  not 
elastic,  its  color  is  usually  dark  green,  and  it  feels  a  little 
greasy.     It  is  often  fine  granular. 

4.  Hornblende  and  Pyroxene. — Hornblende  and  pyroxene 
are  silicates  of  magnesium,  calcium  and  iron,  aluminum  not 
being  an  essential  constituent.     The  usual  kind  of  each  in 
rocks  is  black,  or  greenish  black,  and  2.8  to  3.2  in  specific 
gravity ;  but  white   and  light  green  varieties   are   common. 
They   equal   feldspar  in   hardness ;    unlike    mica,  they   are 
brittle.     The  crystals  or  crystalline  grains  have  two  equal 
shining  cleavages ;  in  hornblende  the  angle  between  the  two 
is  about  124°,  in  pyroxene,  87°.     Hornblende  is  often  in 
long  slender  crystallizations,  and  asbestus  is  a  variety  of  it. 
Both  make  hard  and  tough  rocks.     Pyroxene  is  a  constituent 
of  trap,  and  of  a  large  part  of  igneous  rocks. 

5.  Talc ;    Serpentine.  —  Talc   and   .serpentine    are   hydrous 
silicates  of  magnesium.     They  both  \iave   a  greasy   feel, — 
especially  talc.     Talc  is  very  soft,  so  soft  that  it  does  not 
feel  gritty  to  the  teeth.     It  is  often  in  foliated  plates  or 
masses  like  mica ;  but  the  folia,  or  leaves,  though  separating 
rather  easily,  and  flexible,  are  not  elastic.     The  usual  color 
is  pale  green.     Soapstow  or  steatite  is  a  massive  variety  of 
talc,  of  whitish,  grayish,  or  greenish  color. 


24 


STRUCTURAL   GEOLOGY. 


Serpentine.  —  Contains  much  water  (14  per  cent).  It  is 
usually  a  dark-green  massive  mineral  or  rock,  of  a  very 
fine-grained  texture,  and  soft  enough  to  be  cut  with  a 
knife. 

6,  The  following  minerals  occur  distributed  in  crystals 
through  many  crystalline  rocks:  — 

Garnet;  Tourmaline.  —  These  species,  like  the  micas,  are 
aluminum  silicates  of  magnesium,  calcium  and  iron.  Garnet 
is  often  in  dark  red,  brownish,  or  black  crystals  of  12  or  24 


Fig.  9. 


Fig.  10. 


Fig.  11. 


sides  (dodecahedrons  or  trapezohedrons).  The  first  of  these 
forms  is  represented  in  Fig.  9,  showing  garnets  distributed 
through  a  mica  schist.  Tourmaline  (Fig.  10)  is  generally  in 

oblong  3,  6,  9,  or  12-sided  crys- 
tals, shining  and  black;  also  at 
times  blue-black,  brown,  green, 
and  red. 

Andalusite  is   simply  an   alu- 
minum silicate  and  hence  is  in- 
fusible.   It  is  found  in  imbedded 
crystals  in  clay  slate,  and  some- 
times in  mica  schist ;  the  form  is 
nearly  a  square  prism.     The  in- 
terior of  the  crystals  is  very  frequently  black  or  grayish-black 
at  the  centre  and  angles  (Fig.  11),  while  the  rest  is  nearly 
white ;  and  this  variety  is  called  made,  or  chiastolite. 

Cyanite,  —  Has   the   same   composition   as  the  preceding, 


CONSTITUTION  OF  ROCKS.  25 

and  like  it  is  infusible.  Usually  occurs  in  mica  schist  or 
gneiss  in  thin,  blade-like,  pale  blue  crystals. 

Staurolite.  —  Belated  to  the  last  two  minerals,  and  infusible, 
but  it  contains  some  iron.  Its  crystals  are  stout  prisms  of 
128,°  of  black  or  brown  color ;  they  often  have  the  form  of 
a  cross,  whence  the  name,  from  crtaupo?  a  cross. 

3.  CARBON.  —  Carbon  occurs  pure  among  minerals  only  in 
diamond  and  yraphitc.  It  is  the  chief  element  in  mineral 
coal,  but  is  combined  in  it  with  more  or  less  of  hydrogen  and 
oxygen,  and  also  some  nitrogen.  Charcoal,  the  carbo  of  the 
Romans,  is  nearly  all  carbon. 

1.  Diamond ;  Graphite.  —  Diamond  and  graphite  are   both 
pure  carbon,  but  in  different  molecular  states ;  the  former, 
the   hardest   of    minerals,   crystallizing    in   octahedral    and 
related  forms  ;   the  latter,  one  of   the   softest,  crystallizing 
in  hexagonal  plates,  with  nearly  the  easy  cleavage  of  mica 
and  the  lustre  of  steel.      Graphite  is  also  called  plumbago 
and  black-lead,  and  is  the  material  of  the  mis-named  lead- 
pencils.     It  occurs  in  crystalline  rocks  in  scales  and  masses, 
and  is  ground  up  and  subjected  to  pressure  to  prepare  it  for 
making  pencils. 

2.  Mineral  Coal ;  Mineral  Oil.  —  Mineral  coal  is  not  a  true 
mineral.      It   constitutes   beds   in  various   rock-formations, 
and   has   been   formed   from  wood  or   some   kind  of  vege- 
table material.     There  are  three  prominent  kinds,  differing 
in  the  amount  of  oxygen  and  hydrogen  that  is  present  with 
the  chief  ingredient  carbon,  and  consequently  in  the  amount 
of  inflammable  gas  given  out  on  burning.     This  gas  gener- 
ally consists  simply  of  carbon  and  hydrogen,  and  is  largely 
the  carbo-hydrogen  used  in  illumination. 

1.  Anthracite    contains    over  85  per  cent  of  carbon.      It 
yields  little  that  is  volatile,  and  burns  with  a  feeble  blue 
flame. 

2.  Bituminous  Coal  has  less  hardness  and  lustre  than  an- 
thracite, contains  usually  70  to  80  per  cent  of  carbon,  and 
gives  out  on  heating  20  to  40  per  cent  of  volatile  matter.     It 


26  STRUCTURAL   GEOLOGY. 

hence  burns  with  a  bright  yellow  flame.  It  is  the  source 
of  illuminating  gas,  and  will  yield  also  mineral  oil.  Cannel 
coal  is  a  compact  bituminous  coal  having  a  feeble  lustre; 
it  often  yields  40  to  50  per  cent  of  volatile  matter,  and  is  an 
available  source  of  mineral  oil.  Bituminous  coal  is  called 
caking  coal  when  it  softens  in  the  fire  and  cakes  at  surface, 
so  that  a  fire  made  of  it  requires  poking  to  make  it  burn 
freely ;  non-caking  kinds  have  not  this  quality,  and  hence  are 
preferable  for  fuel  and  economical  purposes. 

3.  Brown  Coal  differs  from  bituminous  coal  in  its  brownish- 
black  powder,  and  in  containing  2  or.  3  times  as  much  oxygen 
(15  to  25  or  more  per  cent).     The  mineral  coal  from  rocks 
more  recent  than  the  true  Carboniferous  formation  is  often 
improperly  called  brown  coal,  even  when  good  bituminous 
coal,  without  a  brownish  color  to  the  powder.     The  name 
lignite  is  sometimes  also  applied  to  it ;  but  true  lignite  is 
coal  that  retains  the  fibrous  texture  of  the  original  wood. 

4.  Mineral  Oil  is  liquid  carbo-hydrogen,  and  is  chemically 
related  to  illuminating  gas.     It  was  formed  out  of  animal  or 
vegetable  materials.     Illuminating  gas  is  often  produced  in 
great  quantities  from  the  wells  or  sources  yielding  mineral 
oil,  and  in  some  villages  in  oil  regions  the  houses  are  heated 
and  lighted  by  it.      Many  black   shales  yield  mineral   oil 
when  heated.      They  do  not  contain  the  oil,  but  instead  a 
peculiar   carbo-hydrogen   compound  (not  yet   satisfactorily 
investigated)  which  yields  the  oil  on  heating.     Mineral  oil 
on  long  exposure  to  the  air  combines  with  oxygen  and  finally 
becomes  a  black  fusible  bitumen,  or  a  coal-like  substance 
having  little  or  no  fusibility. 

3.  Carbonic  Acid,  or  Carbon  dioxide  (C  02),  is  a  gas  contain- 
ing 27.65  per  cent  of  carbon  and  the  rest  oxygen.  It  con- 
stitutes 3  out  of  10,000  parts  by  volume  of  the  atmosphere, 
and  is  carried  from  the  atmosphere  to  the  earth  by  the  rains. 
It  is  formed  in  the  combustion  of  wood,  combustion  consist- 
ing chiefly  in  the  combining  of  oxygen  with  the  constituents 
of  the  wood.  It  is  also  given  out  in  the  respiration  of 


CONSTITUTION  OF   ROCKS. 


27 


animals,  the'  processes  of  life  in  animals  being  carried  forward 
through  a  sort  of  combustion,  or  a  similar  combination  of 
oxygen  with  the  materials  of  the  tissues. 

4.  CARBONATES.  —  Compounds  containing  the  elements  of 
carbonic  acid  or  carbon  dioxide  with  those  of  lime,  magnesia, 
etc. 

1  Calcite,  or  Calcium  carbonate  (Ca  C  03). —  The  material 
of  limestone  and  marble.  It  crystallizes  in  many  forms,  a 
few  of  which  are  represented  in  Figs.  12,  13.  Its  colors  are 
very  various.  It  cleaves  easily  in  three  directions  with 
bright  surfaces,  as  may  be  seen  on  examining  even  the  grains 
of  a  fine  white  marble.  It  is  so  soft  as  to  be  easily  scratched 
with  a  knife ;  dissolves  in  diluted  acid  (hydro-chloric)  with 
effervescence,  that  is,  with  an  escape  of  carbonic  acid  gas ; 
and  when  heated  (as  in  a  lime-kiln  or  before  the  blow-pipe") 
it  burns  to  quick-lime  without  melting.  By  its  effervescence 
with  acids  it  differs  from  all  the  minerals  before  mentioned. 


2.  Dolomite,  calcium-magnesium  carbonate  (|-Ca  .]  Mg  C  03); 
that  is,  it  differs  from  calcite  in  containing  magnesium  in 
place  of  half  of  the  calcium.  Very  much  of  the  so-called 
limestone  of  the  world  is  magnesian  limestone.  It  closely  re- 
sembles common  limestone,  but  may  often  be  distinguished 
by  its  effervescing  scarcely  at  all  with  acid  unless  heat  be 
applied.  The  trial  may  be  made  by  dropping  a  particle,  las 


28  STRUCTURAL  GEOLOGY. 

large  as  half  a  grain  of  wheat,  into  a  test-glass*  containing 
a  mixture,  half  and  half,  of  hydro-chloric  acid  and  water. 
For  iron-carbonate  (siderite)  see  next  page. 

5.  CHLORIDES. — The  only  chloride  forming  rock-masses  is 
Common  or  Rock  Salt  —  It  is  sodium  chloride  (Na  Cl).     It  is 

easily  distinguished  by  its  taste.  It  constitutes  beds,  more 
or  less  impure,  in  strata  of  various  ages  from  the  Silurian  to 
recent  time ;  which  is  accounted  for  by  the  fact  that  the 
universal  ocean  is  its  source,  and  simple  evaporation  the 
means  of  depositing  it.  Silurian  rock  salt  occurs  in  "Western 
New  York  and  Canada ;  and  a  great  recent  (early  Quater- 
nary) deposit,  nearly  40  feet  thick  and  remarkably  pure, 
occurs  at  Petit  Anse,  La.,  near  the  Gulf  of  Mexico.  The 
saline  constituents  of  the  ocean's  waters  constitute  about 
3.53  parts  in  100  ;  of  which  three-fourths  or  2.65  are  common 
salt,  the  rest  being,  —  magnesium  chloride  0.32,  magnesium 
sulphate  0.19,  potassium  chloride  0.12,  calcium  sulphate,  or 
gypsum,  0.16,  sodium  bromide  0.  06r=3.53,  with  traces  also 
of  other  ingredients. 

6.  IRON  ORES.  —  Iron  ores  are  widely  distributed  in  rocks, 
and  some  of  them  form  thick  beds.     Unlike  the  minerals 
mentioned  above   they  have   a   specific   gravity    above  3.5. 
The  most  important  are  three  oxides,  two   sulphides,  and  a 
carbonate. 

1.  Hematite,  or  iron  sesquioxide  (Fe2  03).     It  yields  a  red 
powder,  whence  its  name  given  it  by  the  old  Greeks,  from 
al/jia  Hood.      Its  crystals   have  usually  an  iron-black  color, 
and  high  lustre ;  but  it  is  deep  red  when  earthy  or  impure. 
It  is  the  source  of   the  color  in  red  sandstones  and  other 
red  rocks. 

2.  Limonite,  or  hydrous  iron-sesquioxide,  equivalent  to  2  of 
Fe2  03  to  3  parts  of  water.     It  has  a  brownish-yellow  powder. 
It  varies  in  color  from  black  to  brown  and  yellow.    While  red 
ochre  of  painters  is.  impure  hematite^  yellow  ochre  is  impure 
limonite.     Limonite  is  the  coloring/mgredient  in  a  large  part 
of  the  brown  and  brownish  yellow  rocks  and  clays.     The 


KINDS   OF  ROCKS.  29 

water  present  goes  off  on  heating  and  hence  the  mineral,  and 
all  rocks  colored  by  it,  when  heated  turn  red.  It  is  formed 
from  the  oxidation  of  various  iron-bearing  minerals  (page  82), 
and  often  makes  deposits  in  marshes,  whence  its  name  from 
the  Greek  for  marsh. 

3.  Magnetite.  —  Magnetite   has    an   iron-black    color,  like 
hematite ;  but  it  is  attracted  by  a  magnet,  and  has,  besides, 
a  black  powder.      It   consists  of  3   of  iron  to  4  of    oxygen 
(Fe3  04).     It  is  common  in  grains  in  a  large  part  of  rocks,  the 
calcareous  (or  limestones)  excluded,  and  among  the  sands  of 
seashores  and  soils ;  and  like  hematite,  constitutes  great  beds 
in  some  of  the  older  rocks. 

Iron  protoxide  never  occurs  as  a  mineral. 

4.  Pyrite.  —  An  iron-sulphide,  (Fe  S2)  of  a  brass-yellow  color 
and  as  hard  nearly  as  quartz.     It  will  strike  fire  with  a  steel, 
and  was  named  by  the  Greeks  from  irvp,  fire.    It  is  common  in 
rocks,  in  massive  forms,  crystals  (often  cubes),  and  in  grains. 
Pyrrlwtite  is  the  name  of  another  common  iron-sulphide  con- 
taining proportionally  less  sulphur  (Fe7  S8),  having  the  grayish 
yellow  color  of  bronze,  and  so  soft  as  to  be  easily  scratched 
with  the  point  of  a  knife. 

5.  Siderite,  or  iron  carbonate  (Fe  C  03),  called  also  spathic 
iron.     It  has  approximately  the  cleavage  and  form  of  calcite 
when  crystallized,  but  is  usually  grayish  in  color.    It  changes 
readily  on  exposure  to  brown  (and  to  limonite),  and  is  much 
heavier  than  calcite,  its  specific  gravity  being  3.7  to  3.9.     It 
effervesces  in  heated  dilute  hydro-chloric  acid,  like  dolomite. 

The  "  iron-stone  "  or  "  clay  iron-stone  "  of  coal  regions  and 
others,  used  as  an  ore  of  iron,  is  very  often  siderite ;  but  it  is 
often  also  hematite,  and  sometimes  limonite. 

2.  Kinds  of  Rocks. 

1.  Fragmental  and  Crystalline  Rocks.  —  The  minerals  of 
which  a  rock  consists  may  be  either  (1)  in  broken  or  worn 
grains  or  pebbles,  like  those  of  sand  or  mud  or  a  bed  of  gravel ; 
or,  on  the  contrary,  (2)  they  may  be  in  crystalline  grains,  in 


30  STRUCTURAL   GEOLOGY. 

which  case  they  were  formed  where  they  now  are  at  the  time 
of  the  crystallization  of  the  rock.  Such  crystalline  grains  are 
angular,  as  may  be  seen  on  a  surface  of  fracture,  and,  in-  the 
case  of  most  minerals  excepting  quartz,  show  surfaces  of 
cleavage.  Common  white  marble  and  granite  are  good 
examples  of  rocks  having  a  crystalline  texture ;  and  also 
loaf-sugar  and  steel,  among  products  of  art. 

The  rocks  of  the  first  kind,  consisting  of  fragments  of 
other  rocks,  are  called  fragmental  rocks ;  and  those  of  the 
latter  kind,  crystalline  rocks. 

2,  Fragmental  rocks.  —  These   are    the   most   common   of 
rocks.      They  constitute  the  chief  part  of  the  twenty  miles 
of  beds,  in  depth  (page  1),  open  to  geological  study.      The 
wear  and   decomposition  of   the  oldest  rocks  produced  the 
fragmental  material  for  those  of  the  next  age,  and  so   on 
through  geological  time;  and  the  rocks  made  of  such  ma- 
terial, as,  for  example,  sandstones,  shales,  and  conglomerates, 
are  the  fragmental  rocks.     They  are  stratified  rocks  also,  be- 
cause they  are  in  beds.     They  are  also  called  sedimentary 
rocks,  because  the  material  was  in  most  cases  deposited  as  a 
sediment  from  waters.     Most  limestones  also  are  fragmental 
rocks,  as  explained  on  page  31. 

Intermediate  between  rocks  that  are  obviously  fragmental 
and  crystalline  there  are  others,  of  a  flinty  compactness,  which 
show  no  distinct  grains,  and  are  therefore  not  easily  referred 
to  either  division.  To  determine  the  division  to  which 
such  rocks  belong,  the  beds  affording  them  and  others  associ- 
ated have  to  be  studied.  If  these  associated  rocks  are  frag- 
mented, then  the  compact  beds  are  probably  so  also ;  but  if 
these  are  crystalline,  then  they  are  probably  related  to  the 
crystalline.  Experience  among  rocks  is  required  to  decide 
correctly  in  all  such  cases.  The  examination  of  thin  trans- 
parent slices  with  the  microscope  is  sometimes  the  only 
means  of  distinguishing  the  two  kinds. 
'  The  crystalline  rocks  are  either  mttamorphic  or  igneous. 

3.  Metamorphic  rocks  are  those  which  have  been  changed 


KINDS  OF   ROCKS.  31 

(metamorphosed)  into  crystalline  rocks,  and  usually  without 
fusion.  The  rocks  so  changed  are  the  ordinary  fragmental 
rocks  and  limestones.  The  alteration,  when  most  perfect, 
has  consisted  in  a  complete  crystallization  of  the  rock,  and, 
when  least  so,  in  its  consolidation  ;  between  which  extremes 
all  gradations  exist.  Examples  of  metamorphic  rocks  are 
architectural  marble,  mica  schist,  gneiss^aad  much  gran|te. 

4.  Igneous  rocks   are   those  which  have  come  up    melted 
through  volcanic  vents,  or  through  fissures   opened  to  some 
seat  of  melted  rock  within  or  below  the  earth's  crust.     They 
include  lavas,  part  of  porphyry  and  granite,  and  other  rocks 
described  beyond  (page  37). 

It  appears  from  the  definitions  above  given  that  the  frag- 
mental rocks  have  come  from  the  working  over  and  redistri- 
bution of  surface  rock-material ;  and  the  metamorphic,  from 
the  crystallizing  in  certain  regions,  through  some  means,  of 
fragmental  rocks.  Of  the  three  kinds,  igneous  rocks  alone 
have  added  to  the  amount  of  surface  material.  Besides 
these,  many  veins  contain  mineral  material  from  the  earth's 
depths. 

5.  Calcareous  rocks.  —  Calcareous  rocks,  so  named  from  the 
Latin  calx  lime,  are  the  limestones.    To  a  great  extent  they  are 
of  organic  origin,  that  is,  have  been  formed  from  pulverized 
animal  relics,  such  as  shells  and  corals ;  and  in  this  case  they 
are  properly  fragmental   or  sedimentary  beds,  although   so 
finely  compact  that  this  might  not  be  suspected  from  their 
texture. 

Some  limestones  have  been  made  from  the  accumulation 
and  consolidation  of  minute  shells,  called  Rhizopods.  These 
shells  being  generally  no  larger  than  grains  of  sand,  powder- 
ing was  not  necessary.  The  limestone  rocks  formed  of  them . 
hence  may  not  be  fragmental.  Still,  even  these  minute  shells 
are  generally  broken.  Chalk  is  an  example. 

Limestones  of  mineral  origin,  that  is,  those  made  from 
earlier  limestones,  occur,  but  are  not  very  common.  Lime- 
stone conglomerates  are  of  this  kind. 


32  STRUCTURAL  GEOLOGY. 

Other  calcareous  rocks  have  been  deposited  from  viaters 
holding  the  material  in  solution,  and  are,  therefore,  of  chemical 
origin.  Of  this  kind  is  the  travertine  of  Tivoli  near  Kome  in 
Italy,  and  of  Gardiner's  Eiver  in  the  geyser  region  of  the 
Yellowstone  Park,  and  similar  beds  in  many  regions  of 
mineral  springs,  besides  the  petrified  moss  and  trees  of  some 
marshy  places. 

6.  Siliceous  rocks.  —  Siliceous  rocks  are  those  that  consist 
largely  of  quartz,  or  silica.     The  name  is  from  the  Latin  silex, 
signifying  flint,  a  variety  of  quartz.     Siliceous  material,  or 
quartz,  like  the  calcareous,  is,  as  stated  on  page  21,  of  both 
mineral  and  organic  origin  ;  but  the  mineral  is  vastly  the 
most  abundant.     It  is  also  to  a  small  extent  a  chemical  pro- 
duct, as  in  the  siliceous  depositions  about  geysers  (page  142). 
The  silica  of  organic  and  chemical  origin  is  usually  in  the 
state  of  opal-silica.     Opal-silica  has  less  hardness  and  specific 
gravity  than  quartz ;  but  by  solution  and  consolidation,  gener- 
ally becomes  true  quartz,  as  in  flint. 

7.  Hydrous  rocks.  —  A  hydrous  mineral  is  one  containing 
water  ;  and  a  hydrous  rock  contains  a  hydrous  mineral  among 
its  constituents  (page  23). 

8.  Porphyritic  rocks. — A  porphyritic  rock  is  one  having  dis- 
tinct crystals  of  feldspar  disseminated  through  it,  so  that, 
when   polished,  the  surface   appears   spotted  with  a  light- 
colored  mineral,  usually  between  an  eighth  of  an  inch  and 
two  inches  in  length.      The   red   porphyry   of   Egypt   and 
the  green  porphyry  of  the  eastern  borders  of  Greece,  much 
used  for  ornamental  purposes  by  the  ancients,  are  typical 
examples.     Granite,  gneiss,  syenite,  diorite,  and  other  rocks 
are  said  to  be  porphyritic  when  similarly  spotted. 

9.  Massive,  schistose,  laminated,  slaty,  shaly  rocks,  —  Kocks 
are  termed  massive  when  there  is  no  tendency  to  break  into 
slabs  or  plates,  as  in  the  case  of  granite  and  most  conglom- 
erates ;   schistose,   if    crystalline,   when   breaking   into  slabs 
or  plates,  owing  to  the  arrangement  in  layers  of  the  mineral 
ingredients,  especially  the  mica  or  the  hornblende ;    lami- 


KINDS  OF  ROCKS.  33 

netted,  when  splitting  into  slabs  or  flagging-stones,  but  not  in 
consequence  of  a  crystalline  structure ;  slaty,  when  dividing 
easily  into  thin,  even,  hard  slates,  like  roofing  slate ;  sJialy, 
when  dividing  easily  into  thin  plates  like  slate,  but  the 
plates  irregular  and  often  fragile. 

The  term  schist  is  applied  to  a  schistose  rock ;  flag,  to  a 
laminated  rock  ;  slate,  to  a  slaty  rock  ;  shale,  to  a  shaly  rock. 

The  kinds  of  rocks  are  here  described  under  the  four  heads  : 
1.  Fragmental  Rocks,  not  calcareous;  2.  Metamorphic  Rocks, 
not  calcareous  ;  3.  Calcareous  Rocks ;  4.  Igneous  Rocks. 

I.  Fragmental  Rocks,  not  Calcareous. 

The  fragmental  material  which  the  wear  and  decomposi 
tion  of  rocks  ordinarily  produces  is  either:  (1)  sand ;  (2 
gravel ;  (3)  mud,  or  earth:  or  (4)  clay ;  or  mixtures  of  these 
materials.    Hence  these  are  the  constituents  of  the  fragmental 
rocks,  and  they  determine  their  kinds. 

1.  Sand-beds;  Gravel-beds.  —  Most  sand  or  gravel  consists 
chiefly  of  quartz ;  but  some  beds  are  made  of  granite  sand 
or  pebbles,  or  of  fragments  of  other  rocks.     Some  contain 
much  clay,  or  are  argillaceous  (so  named  from  argilla,  clay^ ; 
some  are  red  or  brownish  yellow,  owing  to  the  presence  of 
iron-oxide,  and  are  hence  ferruginous.     Some  will  effervesce 
slightly  with  acid,  and  are  hence  calcareous  (page  31).     Beach 
sands  often  contain  red  grains  of  garnet ;  and  commonly  black 
grains  of  magnetite,  which  a  magnet  easily  attracts. 

2.  Mud ;  Earth ;  Clay.  —  Mud   and  earth  contain,  besides 
grains  of  quartz,  some  pulverized  feldspar,  or  else  clay,  with 
more  or  less  of  other  minerals.     The  terms  argillaceous*,  fer- 
ruginous, calcareous,  are  here  applied  as  above  ;  the  calcareous 
grains  are  usually  derived  from  the  grinding  up  of  shells. 
When  Hack  the  color  is  due  to  carbonaceous  material  derived 
from  vegetable  or  animal  decomposition. 

Common  clay  is  a  mixture  of  pure  clay  with  grains  of 
quartz,  feldspar,  and  usually  traces  of  hydrous  iron-oxide, 

3  . 


34  STRUCTURAL   GEOLOGY. 

(limonite),  or  else  iron-carbonate.  Owing  to  the  iron,  it  burns 
red,  making  red  brick — heat  changing  the  iron-mineral  present 
to  hematite  (page  28).  Occasionally,  as  in  certain  Milwau- 
kee clays,  the  iron  is  in  an  iron-silicate,  so  that  the  heat 
cannot  oxidize  it ;  and  consequently  the  brick  it  makes  are 
not  red.  Clays  free  from  iron  are  required  for  white  pottery ; 
and  free  also  from  grains  of  feldspar  for  making  ^re-brick, 
because  the  potash  of  feldspar  makes  clay  fusible. 

Pure  clay,  or  Imolin,  is  white,  and  feels  greasy.  It  is  an 
aluminum  silicate  containing  14  per  cent  of  water.  It  results 
from  the  decomposition  of  feldspar  (page  84).  It  is  used  in 
making  fine  pottery  and  porcelain,  and  paper. 

3.  Sandstone.  —  A  rock  made  of  sand,  of  red,  gray,  brown, 
white  and  other  colors.     When  of  quartz  sand  it  is  a  quart- 
zose  or  siliceous  sandstone ;  if  of  granite  sand,  a  granitic ;  if 
fine  earthy  or  clayey,  an  argillaceous  sandstone.     It  makes 
a  durable  building  stone  when  firm,  if  not  much  absorbent 
of  water  when  immersed  in  it,  and  if  free  from  pyrite  so  as 
not  to  rust  on  exposure.     The  brownish  red  is  often  called 
freestone.    The  sandstone  used  for  grindstones  is  even-grained 
and  more  or  less  friable. 

4.  Conglomerate. — Consolidated  gravel.      If  the  stones  are 
rounded  the  rock  is    often    called   a  pudding-stone;    and  if 
angular  fragments,  a  breccia  ;  if  the  pebbles  are  of  quartz,  a 
siliceous  conglomerate ;  if  of  limestone,  a  calcareous  conglome- 
rate.    The  stones  may  be  a  foot  or  more  in  diameter,  though 
usually  much  smaller. 

5.  Shale,  —  A  somewhat  slaty  rock  made  of  clay  or  clayey 
earth  or  fine  mud.     The  colors  are  of  all   dull  shades  from 
gray  to  red  and  black.      Carbonaceous  shale  is  the  blackish 
kind,  yielding  mineral  oil  when  heated. 

6.  Tufa. —  A  volcanic  sandstone,  composed  of  volcanic  sand 
or  pulverized  volcanic  rocks :  the  color  is  usually  brownish, 
brownish-yellow,  grayish,  or  reddish. 


f  OF  TM6  \ 

VUlVKKSfTY    t 
KINDS  OF  ROCKS.  35 


2.    Metamorphic  Rocks. 

1.  Granite,  —  A  crystalline  rock,  consisting  of  quartz,  feld- 
spar, and  mica.     Color,  usually  light  or  dark  gray,  or  flesh- 
red,  the  latter  shade  derived  from  a  flesh-colored  feldspar : 
the  quartz,  uncleavable  and  usually  grayish-white  in  color ; 
the  feldspar,  white  to  flesh-red,  and  yielding  smooth,  shining 
surfaces  by  cleavage;  the  mica,  white  to  black,  and  afford  ing- 
thin,  flexible  leaves  by  cleavage. 

2.  Gneiss.  —  Like  granite  in  constitution,  but  having  a  bed- 
ded structure,   owing  to  the  arrangement  of   the  minerals, 
the  mica  especially  being  in  parallel  planes ;  it  has,  therefore, 
a  banded  appearance  on  a  surface  of  transverse  fracture.     If 
the  color  of  the  gneiss  is  dark  gray,  it  is  banded  usually  with 
black   lines   consisting   largely   of   black  mica.     Along   the 
micaceous  planes  it  breaks  rather  easily  into  slabs,  which  are 
sometimes  used  for  flagging. 

3.  Mica  Schist.  —  Eelated  to  gneiss,  but  consisting   more 
largely  of  mica,  with  usually  more  quartz  and  less  feldspar, 
and,  in  consequence  of  the  mica,  breaking  into  thin  slabs. 
The   slabs  have  a  glistening   surface.     In   regions  of   mica 
schist  the  dust  of  the  roads  is  often  full  of  shining  particles 
of  mica. 

4.  Syenyte ;  Hornblendic  Gneiss ;  Hornhlendic  Schist.  — Syenyte 
resembles  granite,  but  contains   hornblende,  a   black,  brittle 
mineral,  in  place  of  mica.     A  rock  like   gneiss,  but  contain- 
ing hornblende  in  place  of  mica,  is  called  syenyte  gneiss.     A 
black  or  greenish-black   rock   consisting   almost   wholly   of 
hornblende  and  schistose  is  called  hornblende  schist ;  or  if  not 
schistose,  Jiornblendyte. 

5.  Hydromica   Schist.  —  A   slaty,  fine-grained   mica   schist 
feeling  somewhat  greasy  to  the  fingers.     It  used  to  be  called 
talcose  slate ;  but  it  contains  a  hydrous  mica  instead  of  talc. 

6.  Chlorite  Schist.  —  A  slaty  rock  containing  the  olive-green 
mineral  chlorite  (page  23),  (which  gives  it  a  dark  green  color.) 
Much  hydromica  schist  is  chloritic. 


36  STRUCTURAL  GEOLOGY. 

7.  Slate,  Argillyte,  Phyllyte.  —  Names  of  roofing-slate  and 
allied  slaty  rocks.     The  texture  is  hardly  crystalline  to  the 
naked  eye.     The  slates  in  the  most  perfect  kinds  are  hard, 
smooth  in  surface,  and  not  absorbent  of  water.     Color,  blue- 
black,  purplish,  red,  greenish,  and   of  other  shades.     Much 
slate  is  a  hydromica  schist  of  very  fine  grain. 

There  is  a  gradual  passage  of  the  above  rocks  from  granite 
into  gneiss;  from  gneiss  into  mica  schist;  and  from  mica 
schist,  hydromica  schist,  and  chlorite  schist  into  argillite. 

8.  Quartz  Rock;  Quartzyte.  —  Names  applied  to  the  sand- 
stone of  a  rnetamorphic  region.     Quartzyte  is  usually  very 
hard.     It  differs  from  massive  quartz  in  consisting  (as  seen 
under  a  lens)  of  grains  of  quartz.      Itacolumite  or  flexible 
sandstone,  is  a  laminated  porous  quartzite  containing  minute 
scales  of  a  hydrous  mica,  and  having  some  flexibility.    Occurs 
in  the  gold  regions  of  North  Carolina  and  Brazil. 

9.  Dioryte.  —  Near  syenyte ;  but  the  feldspar  is  not  ortho- 
clase,  as  in  syenyte,  but  oligoclase  or  labradorite.     It  is  a 
coarse  or  fine  grained  rock,  grayish  white  to  dark  green  in 
color,  and  sometimes  almost  black. 


3.    Calcareous  Rocks. 

a.    Non-metamorphic. 

1.  Common  Limestone.  —  A  compact  rock  of  grayish  and 
other  dull  shades  of  color  to  black,  consisting  either  of  calcite 
or  dolomite,  but  often  impure  from  the  presence  of  clayey  or 
earthy  material.  It  breaks  with  little  or  no  lustre.  If  con- 
taining fossils  it  is  called  fossiliferous  limestone ;  if  the  fossils 
are  corals,  coral  limestone ;  if  remains  of  crinoids,  crinoidal 
limestone.  For  the  distinctive  characters,  see  page  27.  When 
impure,  and  therefore  good  for  making  hydraulic  lime  (quick- 
lime that  will  make  a  cement  which  sets  under  water),  it  is 
called  hydraulic  limestone.  Chalk  is  a  variety  of  limestone 
soft  enough  to  be  used  for  marking. 


KINDS  OF  ROCKS.  37 

Many  varieties  of  common  limestone  are  polished  and  used 
as  marbles ;  they  have  black,  reddish,  yellow,  gray,  and  other 
colors  ;  kinds  containing  fossil  shells  are  called  shell-marbles. 

2.  Oblyte.  —  A  limestone  consisting  of  concretions  as  small 
as  the  roe  of  fish,  or  smaller, —  whence  the  name,  from  the 
Greek  MOV,  egg.  Oolite  or  oolitic  limestone  occurs  in  all  the 
geological  formations,  and  is  forming  in  modern  seas  about 
the  Florida  keys  and  other  coral  reef  regions. 

3.  Travertine.  —  Stalactites  are  limestone  concretions  hang- 
ing from  the  roofs  of  caverns ;  and  stalagmite  is  the  same 
material  covering  the  floors ;  both  are  formed  from  the  calca- 
reous waters  that  come  through  the  roof,  and  are  sometimes 
called  dripstone.     A  similar  deposit  from  streams  or  ponds  is 
called  travertine ;  it  is  sometimes  used  for  a  building  stone. 
Petrified   leaves  and  moss  are  made   by  the   same  kind   of 
waters. 

b.    Metamorphic. 

Crystalline  Limestone ;  Architectural  and  Statuary  Marble.  - 

Limestone  having  a  crystalline  texture,  and,  consequently, 
glistening  on  a  surface  of  fracture.  A  pure  white  kind,  of  fine 
grain,  is  used  for  statuary,  and  both  this  and  coarser  varieties 
for  marble  buildings.  Most  of  the  clouded  marbles  are  here 
included. 

4.  Igneous  Rocks. 

The  following  igneous  rocks  are  of  two  series  :  I.,  the  Horn- 
blende-pyroxene series,  containing,  besides  the  feldspar,  much 
hornblende  or  pyroxene ;  specific  gravity  above  2.75;  colors 
usually  dark,  from  black  to  red  and  dark  gray.  IT.  The  Feld- 
spathic  series,  the  feldspar  greatly  predominating,  with  little 
or  no  hornblende  or  pyroxene;  specific  gravity  under  2.75  ; 
colors  usually  light  gray  to  red. 

1.  HORNBLENDE-PYROXENE  SERIES.  —  1.  Syenyte  and  Dioryte 
(pp.  35,  36)  occur  as  igneous  rocks  as  well  as  metamorphic. 
The  latter  is  often  a  very  fine-grained  compact  rock,  and  when 


38  STRUCTURAL  GEOLOGY. 

it  contains  disseminated  feldspar  crystals  makes  a  variety  of 
porphyry.  The  red  porphyry  of  Egypt  contains  in  the  mass 
oligoclase  and  hornblende,  and  has  disseminated  crystals  of 
orthoclase.  The  green  porphyry  (or  oriental  verd-antique)  has 
labradorite  and  pyroxene  in  its  compact  mass,  and  hence  is 
more  closely  related  to  the  following  kind,  dolerite.  These 
porphyritic  rocks  are  supposed  to  be  igneous. 

2.  Doleryte  consists  of  the  feldspar  labradorite  and  pyrox- 
ene, and  has  greenish-black,  brownish-black,  and  black  colors. 
It  is   also  often  called  trap.     It  may  be  either  crystalline- 
granular,  or  of  a  flinty  compactness.     It  contains  also  grains 
of  magnetite.    Basalt  is  a  compact  variety.    Diabase  is  another 
name   for  doleryte,  used  especially  for  doleryte  older  than 
Tertiary.     Chloritic  doleryte  is  sometimes  called  melaphyre. 

3.  Peridotyte  is  a  doleryte  containing  grains  of  a  green  sili- 
cate, of  a  bottle-glass  green  color,  called  chrysolite  or  olivine. 

4.  Amphigenyte.  —  The  common  lava  of  Vesuvius,  contain- 
ing a  white  potash-bearing  mineral,  called  leucite  (which  is 
garnet-like  in  its  form)  instead  of   a  feldspar,  and  with  it 
pyroxene. 

2.  FELDSPATHIC  SERIES.  —  1.  Granite  is  here  included  so  far 
as  it  is  an  igneous  rock. 

2.  Trachyte. — Consists    generally   of    orthoclase   feldspar, 
partly  a  glassy  kind  (sanidin),  and  has  a  rough  surface.    Horn- 
blende is  often  sparingly  present,  and  sometimes  quartz. 

3.  Felsyte.  —  Consists    chiefly  of  orthoclase  feldspar,  like 
ordinary  trachyte,  but  is  without  glassy  feldspar  crystals  and 
has  a  smooth  surface  of  fracture.     Some  quartz  is  often  pres- 
ent.    Felsyte-porphyry  consists  of  orthoclase  in  a  compact  con- 
dition, with  disseminated  crystals  of  the  same  feldspar  of  a 
paler  color ;  so  that  a  polished  surface  is  covered  with  angular 
spots.    The  color  is  often  red  and  the  rock  then  resembles  the 
red  porphyry  mentioned  under  dioryte ;  but  its  specific  grav- 
ity is  under  2.75. 

4.  Lava.  —  Any  rock  that  has  flowed  in  streams  from  a  vol- 
cano, especially  if  it  contains  cavities,  or,  in  other  words,  is 


STRATIFIED   ROCKS.  39 

more  or  less  scoriaceous.  The  most  common  kinds  are 
doleryte,  peridotye,  or  trachyte  in  composition. 

Scoria  is  a  light  lava,  full  of  cavities ;  and  pumice,  a  white 
or  grayish  feldspathic  scoria,  having  the  air-cells  long  and 
slender,  so  that  it  looks  as  if  it  were  fibrous. 

Obsidian  is  volcanic  glass,  and  Pitchstone  and  Pearlstone  are 
rocks  that  have  a  texture  between  that  of  stone  and  glass. 

In  the  cooling  of  melted  rock,  the  mass,  if  the  process 
goes  on  rapidly,  may  become  glass  throughout  with  only  occa- 
sional crystalline  grains  or  stony  points  (called  microlites 
from  their  minuteness)  scattered  through  it.  With  slower 
cooling  the  stony  points  are  more  abundant,  and  may  pre- 
dominate, or  they  may  make  up  the  whole  of  the  mass, 
excepting  perhaps  some  points  which  still  remain  as  glass. 
These  peculiarities  are  detected  only  by  the  microscopic 
investigation  of  thin  slices.  Frequently  the  microscope 
detects  an  arrangement  of  the  grains  in  lines  indicating  the 
flow  of  the  material  when  liquid,  or  what  has  been  called  a 
fluidal  structure. 


II.-CONDITION,  STRUCTURE,  AND  ARRANGE- 
MENT OF  ROOK-MASSES. 

The  rocks  above  described  are  the  material  of  which  the 
great  rock-masses  or  terranes  of  the  globe  consist.  These 
rock-masses  occur  under  three  conditions:  —  1.  The  Strati- 
fied; 2.  The  Unstratificd ;  3.  The  Vein-form. 

1.  The  Stratified  condition.  —  Stratified  rocks  are  those  which 
lie  in  beds  or  strata.  The  word  stratum  (the  singular  of 
strata)  is  from  the  Latin,  and  signifies  that  which  is  spread 
out.  The  earth's  rocky  strata  are  spread  out  in  beds  of  vast 
extent,  many  of  them  being  thousands  of  square  miles  in  area 
and  thousands  of  feet  in  thickness. 

The  stratified  rocks  exposed  to  view  over  the  earth  far 
exceed  in  surface  the  unstratified.  They  are  the  rocks  of 


40  STKUCTUKAL   GEOLOGY. 

nearly  the  whole  of  the  United  States  and  of  almost  all  of 
North  America,  and  not  less  of  the  other  continents.  Through- 
out Central  and  Western  New  York,  and  the  States  south  and 
west,  the  rocks,  wherever  exposed,  are  seen  to  be  made  up  of 
a  series  of  beds.  And  if  the  rocks  are  less  distinctly  strati- 
fied over  most  of  New  England,  it  is,  in  general,  only  because 
the  structure  has  been  partly  obscured  by  the  upturning  and 
crystallization  which  they  have  undergone  since  they  were 
formed. 

Fig.  14. 


The  preceding  figure  represents  a  section  of  the  rocks 
along  the  river  below  Niagara  Falls.  It  gives  some  idea  of 
the  alternations  which  occur  in  the  strata.  In  a  total  height 
of  250  feet  (165  feet  at  the  Falls,  at  F,  on  the  right)  there 
are,  on  the  left,  six  different  strata  in  view,  and  parts  of  two 
others,  the  upper  and  lower,  making  eight  in  all.  Number  1 
is  gray  argillaceous  sandstone ;  2,  gray  and  red  argillaceous 
sandstone  and  shale ;  3,  flagstone,  or  hard  laminated  sand- 
stone ;  4,  reddish  shale  and  shaly  sandstone ;  5,  shale ;  6, 
limestone ;  7,  shale ;  8,  limestone.  Only  two  of  these  strata, 
7  and  8,  are  in  sight  at  the  Falls  (at  F).  The  alternations 
are  thus  numerous  and  various  in  all  regions  of  stratified 
rocks.  Along  the  canon  of  the  Colorado  there  are  in  some 
places  more  than  8,000  feet  of  stratified  beds,  showing  their 
edges  in  lofty  precipices,  and  in  the  mountains  towering 
above  the  adjoining  plains. 

It  must  riot  be  inferred  that  the  earth  is  covered  by  a  reg- 
ular series  of  coats,  the  same  in  all  countries ;  for  this  is  far 
from  the  truth.  Many  strata  occur  in  New  York  that  are 
not  found  in  Ohio  and  the  States  west,  and  many  in  South- 


VEINS.  41 

ern  New  York  that  are  not  in  Northern ;  and  each  stratum 
varies  greatly  in  different  regions,  sometimes  being  limestone 
in  one  and  sandstone  or  shale  in  another. 

A  stratum  is  a  bed  of  rock  including  all  of  any  one  kind 
that  lie  together,  as  either  Nos.  1,  2,  3,  4,  5,  6,  7,  or  8  in  the 
preceding  figure. 

A  layer  is  one  of  the  subdivisions  of  a  stratum.  A  stratum 
may  consist  of  an  indefinite  number  of  layers. 

A  system  includes  all  the  various  kinds  of  strata  that  were 
formed  in  one  age  or  period,  as  the  Carboniferous  system  or 
that  of  the  coal  era.  A  subdivision  of  a  system,  including 
two  or  more  related  strata,  is  often  called  a  series,  or  a  group. 

2.  Unstratified  condition.  —  Unstratified   rocks   are    those 
which  do  not  lie  in  beds   or  strata.     Mountain-masses    of 
granite  are  often  without  any  appearance  of  stratification. 
The  rock  of  the  Palisades,  on  the  Hudson,  stands  up  with  a 
bold  columnar  front,  and  has  no  division  into  layers.     Most 
lavas  of  volcanoes  have  flowed  out  in  successive  streams ; 
and,  consequently,  volcanic  mountains  are  generally  strati- 
fied.    But  in  some  volcanic  regions  the  rocks  rise  into  lofty 
summits  without  stratification.     Although  true  granite  bears 
no  marks  of  proper  stratification,  it  very  often  passes  insensi- 
bly into  gneiss,  which  is  a  stratified  rock ;  and  there  is  evi- 
dence in  this  fact  that  granite  is  often  a  stratified  rock  which 
has  lost  the  appearance  of  stratification  in  consequence  of  the 
crystallization  it  has  undergone. 

3.  Vein-form  condition.  —  When  rocks  have  been  fractured, 
and  the  fissures  thus  made  have  been  filled  with  rock-mate- 
rial of  any  kind,  or  with  metallic  ores,  the  fillings  are  vein- 
form,  and  called  veins.     Veins  are  large  or  small,  deep  or 
shallow,  single  or  like  a  complete  network,  according  to  the 
character  of  the  fractures  in  which  they  were  formed.     They 
may  be  as  thin  as  paper,  or  they  may  be  rods  in  width.    Figs. 
15  to  18  represent  some  of  the  forms.     In  Fig.  15  there  are 
two  veins,  a  and  6;  in  Fig.  16,  a  network  of  thin  veins;  in 
Fig.  17,  two,  a,  a,  of  very  irregular  form, — a  kind  not  uncom- 


42 


STRUCTURAL   GEOLOGY. 


mon,  and  another,  b,  intersecting  one  of  these;  in  Fig.  18,  two 
large  veins,  of  still  more  irregular  character  cross  one  another. 


Fig.  15. 


Fig.  16. 


Fig.  17, 


Fig.  18. 


Fig.  19. 


! 

1 

' 

!;' 

',!' 

fi 

1 

,'  i 
i 

';:; 

''i 

II 

J 

i'ii 

'Si! 

1.' 

i. 

;f 

,1;- 

'!;; 

,  ', 

,  1  1 

.' 

I1 

y 

!', 

'• 

,1 

'III 

,  ; 
l'1'j 

i 

"i 
'i 
'It 

1 

Fig.  20. 


(  . 


Many  veins  have  a  landed  structure,  like  Figs.  19  and  20. 

Many  metallic  veins  are  thus  banded,  and  have  the  ores 
lying  in  one  or  more  bands  alternating  with  other  stony 
bands  consisting  of  different  minerals  or  rock-material,  as 
calcite,  quartz,  fluorite,  etc.,  called  the  ganyue  of  the  ore. 


STRUCTURE   OF   ROCKS.  43 

In  Fig.  20,  representing  a  Cornwall  lode,  the  middle  por- 
tion, I)  c  I,  is  made  up  of  bands  of  agate,  b,  with  two  layers  of 
crystallized  quartz,  c,  at  centre ;  a  is  a  layer  of  quartz ;  b,  a 
band  of  the  copper  ore  of  the  vein,  chalcopyrite 
(copper  pyrites) ;  d,  quartz  with  some  fluorite.  Flg*  21° 

When  fissures  have  been  filled  with  melted  rock, 
they  are  usually  called  dikes ;  they  have  regular 
walls,  and  are  not  banded,  although  sometimes 
the  sides  differ  a  little  from  the  middle.  They 
are  often  transversely  columnar  in  structure;  as 
is  illustrated  in  Fig.  21. 

4.  Relation  of  stratified  and  true  unstratified  rocks  in  the 
earth's  crust.  —  The  relations  of  the  stratified  and  unstratified 
rocks  in  the  earth's  crust  will  be  understood  after  consider- 
ing the  origin  of  the  crust. 

The  crust  is  believed  to  be  the  cooled  exterior  of  a  melted 
globe.  After  the  solidifying  of  the  sphere  at  surface,  the  ocean 
commenced  at  once  to  make  fragmented  stratified  rocks  over 
the  exterior  through  the  wear  of  the  crust-rocks,  and  the 
stratifying  of  the  sand  or  mud  thus  made ;  while  the  contin- 
ued cooling,  going  on  very  slowly,  made  unstratified  rocks 
beneath  this  first  crust  as  its  inner  portion.  The  ocean  thus 
worked  over  and  covered  up  with  strata  nearly  all,  if  not  all, 
the  original  unstratified  crystalline  rocks.  Hence  the  areas 
of  the  unstratified  rocks  that  were  made  in  the  first  solidifi- 
cation of  the  globe  are  of  very  small  extent  over  the  conti- 
nents, if  visible  anywhere. 

Geology  has,  for  its  study,  chiefly  stratified  rocks.  Much 
the  larger  part  of  all  the  facts  in  geological  history  are  de- 
rived from  rocks  of  this  kind,  and  therefore  the  various  details 
with  regard  to  their  structure  and  arrangement  are  of  the 
highest  importance. 


44  STRUCTURAL  GEOLOGY. 

/ 

« 

Stratified  Condition. 
I.  Structure. 

1.  Massive,  laminated,  and  shaly  structures.  —  The  massive 
(Fig.  22,  a),  laminated    (Fig.   22,  &),  and   shaly    (Fig.  22,  c), 
structures  of  layers  have  been  explained  on  page  32.     Sand- 
stone is  in  general  most  perfectly  laminated  when  argilla- 
ceous, or  containing  much  clay  or  fine  earthy  material     The 
same  is  true  of  limestone.     The  flagging  stone  used  in  most 
Eastern  cities  for  walks,  is  an  example  of  a  laminated  sand- 
stone, and  of  flags.      It  is   from   near  Kingston,  N.  Y.,  and 
other  places  on  the  west  side  of  the  Hudson. 

2.  Straticulate  structure.  —  The  layers  of  a  rock,  as  clays, 
shales,  sand-beds,   sandstones,   limestones,   are   often   them- 
selves stratified  in  a  very  thin  manner,  and  while  the  thin 
laminae  separate  easily  in  some  cases  (as  in  many  clay-beds 
and  shales),  they  are  indicated  in  others  only  by  the  banded 
appearance  of  a  surface  of  transverse  fracture.     The  struc- 
ture is  straticulate.     Only  when  the  little  layers  are  separable 
is  the  structure  laminated. 

3.  Beach  structure.  —  The  structure  of  the  upper  part  of  a 
beach  is  illustrated  in  Fig.  22,  d.     Instead  of  being  composed 
of  evenly  laid  material,  it  consists  of  many  irregular  small 
layers  as  deposited  or  thrown  together  by  the  waves  during 
storms.     The  lower  part  of  the  beach  has  an  even  slope  of 
usually  5  to  15  degrees,  and  the  sands  beneath  are  in  beds 
having  the  same  slope. 

4.  Cross-bedded  structure. —  In  Fig.  22,  e,  the  beds  that  are 
obliquely  straticulated  or  laminated  are  examples  of  the  cross- 
bedded  structure.     Such  beds,  which  have   sometimes  great 
extent,  have  resulted  from  the  pushing  along  of  the  bottom 
sands  or  earth  by  currents,  causing  at  first  a  little  elevation 
or  ridgelet,  and  then  depositions  successively  over  the  front 
or  down-stream  slope  of  the  elevation.     They  alternate  with 


STRUCTURE   OF  ROCKS. 


45 


other  layers  that  are  horizontal  in  bedding,  because  the  in- 
flowing tide  alternates  with  the  outflowing,  or  because,  if  of 
fresh-water  origin,  such  streams  vary  in  flow  from  low  water 


Fig.  22. 


to  high.  The  succession  of  beds  in  Fig.  e  has  been  described 
as  the  ebb-and-flow  structure.  It  is  common  in  stratified  drift 
as  a  result  of  river  floods. 

5.  Flow-and-plunge  structure. — Where  the  waves  plunge  heav- 
ily in  connection  with  a  flow  of  tidal  or  other  currents,  the 
obliquely  laminated  layer  is  broken  up  into  wave-like  or 
wedge-shaped  parts,  a  few  feet  or  yards  long,  as  illustrated  in 
Fig.  23.  This  structure  is  common  in  stratified  drift. 

Fig.  23. 


6.  Quaquaversal  or  Wind-drift  structure.  —  Having  the  sub- 
ordinate layers  dipping  in  various  directions,  sometimes  curv- 
ing and  sometimes  straight,  as  shown  in  Fig.  22,  /.  The  hills 
of  sand  formed  by  the  winds  (as  on  a  sea-coast  or  the  shores 
of  large  lakes)  are  usually  thus  stratified.  The  sands  drifted 
over  the  rising  heaps  form  layers  conforming  to  the  outer  sur- 
face, and  so  may  slope  at  all  angles.  In  storms,  the  heaps 
may  be  blown  away  in  part,  and  afterward  be  completed 


46 


STRUCTURAL   GEOLOGY. 


again;  but  the  new  layers  will  conform  to  the  new  outer 
surface,  and  hence  have  a  different  direction.  In  this  way, 
by  successive  destructions  and  re-completions,  a  bed  of  sand 
may  be  made  which  shall  consist  of  parts  sloping  in  one 
direction  and  other  parts  in  directions  very  different,  with 
numerous  abrupt  transitions,  as  illustrated  in  the  figure. 


Fig.  24. 


Fig.  25. 


7.  Ripple-marks.  —  A  gentle  flow  of  water,  or  its  vibration, 
over  mud  or  sand,  ripples  the  surface.     The  lighter  winds 
also  make  ripples  over  fields  of  sand.     Layers  of  sandstone 
and  clayey  rocks  are  often  covered  with  ripple-marks  (Fig. 
24). 

8.  mil-marks. — When  the  waters  of  a  spreading  or  return- 
ing wave  on  a  gently  sloping  beach  pass  by  shells  or  stones 
lodged  in  the  sand,  the  rills  furrow  out  little  channels.     Fig. 
25  shows  such  rill-marks  alongside  of  shells  (Lingulse)  in  a 
Silurian  sandstone. 

9.  Mud-cracks,  earth-cracks.  —  When  a  mud-flat  is  exposed 
to  the  air  or  sun  to  dry,  it  becomes  cracked  to  a  few  inches  or 
feet  in  depth.     Fig.  26  represents  mud-cracks  in  argillaceous 
sandstone.     Such  cracks  may  subsequently  become  filled  with 
stony  material,  either  sediment  or  material  in  solution ;  and 


STKUCTURE   OF   ROCKS. 


47 


as  such  fillings  are  often  made  harder  than  the  rock  itself 
they  may  stand  as  prominent  ridges  above  a  weathered  surface 
of  the  rock.  It  is  actually  a  network  of  veins,  but  of  very 
shallow  veins  that  were  filled  from  above.  In  regions  of 
long  droughts,  the  earth-cracks  over  prairies  and  alluvial 
flats  are  sometimes  many  and  deep,  and  over  a  foot  wide. 


Fig.  26. 


Fig.  27. 


Fig.  28. 


10.  Rain-prints  (Fig.  27). —  The   impressions  of   the  large 
rain-drops  of  a  short  shower  made  on  a  half-dry  mud,  have 
often  been  preserved  in  the  rocks. 

11.  Concretionary  structure.  —  Layers    often   contain   small 
spheres  or  disks  of  rock,  which  are  called  con- 
cretions.    They  result  from  a  tendency  in  mat- 
ter  to   concrete   or   solidify   around   centres. 

Some  are  no  larger  than  grains  of  sand,  or  the 
roe  of  fish,  as  in  oolitic  limestone  (page  37). 
Others  are  as  large  as  peas  or  bullets,  and 
others  a  foot  or  more  in  diameter. 

Fig.  28  represents  a  spherical  concretion ;  Fig.  29  a  rock 
made  up  of  rounded  concretions,  having  a  concentric  struc- 
ture ;  Fig.  30,  one  with  flattened  or  disk-shaped  concretions. 

Concretions  are  usually  spherical  in  massive  sandstones. 
lenticular  in  laminated  sandstones  or  clays,  and  flattened  disks 


48 


STRUCTURAL   GEOLOGY. 


in  argillaceous  rocks  or  shales.  All  these  kinds  are  shown  in 
Fig.  31.  The  balls  are  sometimes  hollow,  and  the  disks  mere 
rings.  Frequently  the  concretions  have  a  shell  or  other 
organic  object  at  centre  (Fig.  32).  They  are  often  cracked 


Fig.  29. 


Fig.  30. 


Fig.  31. 


through  the  interior  (Fig  33)  from  drying  (some  soft  clayey 
muds  contracting  to  a  tenth  of  their  bulk) ;  the  outside  in 
such  a  case  solidified  while  the  inside  was  still  moist.  The 
cracks  may  afterward  become  filled  with  other  minerals. 


Fig.  32. 


Fig.  33. 


Fig.  34. 


Fig.   35. 


Sometimes  they  contain  a  loose  ball  within,  —  a  concretion 
within  a  concretion.  A  cavity  lined  with  crystals  (Fig.  34)  is 
called  a  geode.  But  the  hollow  balls  so  lined  within  are  not 
generally  true  concretions. 

12.  Columnar  forms  from  con- 
traction. —  a  more  or  less  perfect 
columnar  structure,  due  to  con- 
traction on  cooling,  is  exemplified 
often  by  igneous  rocks,  as  repre- 
sented in  Fig.  35  and  Fig.  119, 
of  page  145.  The  columns  have 
frequently  transverse  fractures, 
but  the  fractures  are  usually  less 


STRUCTURE   OF  ROCKS.  49 

regular  than  in  the  preceding  figure ;  in  many  cases  the  top 
of  the  sections  of  a  column  is  concave  upward,  but  often  flat 
and  sometimes  convex.  The  structure  is  sometimes  found  in 
sandstone  that  has  been  heated,  but  generally  the  fracturing 
so  produced  is  very  irregular. 

13.  Jointed  structure,  —  The  rocks  of  a  region  are  often  di- 
vided very  regularly  by  numerous  straight  planes  of  fracture, 
the  most  of  them  parallel  to  one  another,  and  cutting  through 
vertically  or  at  large  angles  to  great  depths.  Such  deep  planes 
of  fracture  may  characterize  the  rocks  over  areas  hundreds 
of  miles  in  extent.  They  are  called  joints ;  and  a  rock  thus 
divided  is  said  to  present  a  jointed  structure.  In  many  cttses 
there  are  two  systems  of  joints  or  divisional  planes  in  the 

Fig.  36. 


same  region,  crossing  one  another,  and  the  undermining  of 
a  bluff  of  jointed  beds  and  tumbling  down  of  masses  leads 
to  the  production  of  forms  like  those  of  fortifications  or 
broken  walls,  as  shown  in  Fig.  36, — representing  a  view 
on  the  shores  of  Cayuga  Lake.  The  directions  of  such  joints 
are  facts  which  the  geologist  notes  down  with  care. 

14.  Slaty  cleavage.  —  The  term  slaty  has  been  explained  on 
page  33.  But  one  important  fact,  not  there  stated,  is  that 
the  slates  are  often  transverse  to  the  bedding,  that  is,  they 
often  cross  the  layers  of  stratification  more  or  less  obliquely, 
instead  of  conforming  to  the  layers  or  bedding  like  the  shaly 
structure.  Slaty  cleavage  is  in  this  respect  like  the  jointed 
structure;  but  it  has  the  planes  of  fracture  or  divisional 

4 


50 


STRUCTURAL   GEOLOGY. 


planes  so  numerous  that  the  rock  divides  into  slates  instead 
of  blocks ;  and  the  two  differ  in  mode  of  origin.  Slaty  cleav- 
age is  confined  to  fine-grained  rocks.  In  Fig.  37  the  lines  of 
bedding  or  stratification  are  shown  at  a,  b,  c,  d,  while  the 


Fig.  37. 


Fig.  38. 


transverse  lines  correspond  to  the  direction  of  the  slates.  The 
same  is  shown  in  Fig.  38  with  the  addition  of  a  slight  irreg- 
ularity in  the  slates  along  the  junction  of  two  lasers. 


2.  Positions  of  Strata. 

1.  Original  position  of  strata,  —  horizontal  position.  —  Ordi- 
dinary  stratified  rocks  were  once  beds  of  sand  or  earth,  or  of 
other  rock-material,  spread  out  by  the  currents  and  waves  of 
the  ocean,  or  the  waters  of  lakes  or  rivers,  or  by  the  winds. 

When  the  larger  portion  of  the  beds  over  the  North  Amer- 
ican continent  were  formed,  the  continent  lay  to  a  great 
extent  beneath  the  ocean,  as  the  bottom  of  a  great,  though 
mostly  shallow,  continental  sea.  The  principal  mountain- 
chains  —  the  Eocky  Mountains  and  the  Appalachians  —  had 
not  yet  been  made,  and  the  surface  of  the  submerged  land 
was  nearly  flat.  The  fact  (1)  that  those  beds  were  really 
marine  is  proved  by  their  containing,  in  most  cases,  marine 
shells,  crinoids,  or  corals,  the  relics  of  marine  life ;  and  (2) 
that  the  continental  seas  had  great  extent,  by  the  fact  that 
the  beds  cover  surfaces  tens  of  thousands  of  square  miles  in 
area,  some  of  them  reaching  from  the  Atlantic  border  west- 
ward beyond  the  Mississippi.  In  the  large  continental  seas, 
the  deposits  made  by  means  of  the  currents  and  waves  were 
;  nearly  or  quite  horizontal.  As  they  increased,  they  would  near 


POSITIONS   OF  STRATA. 


51 


the  surface ;  and  here  the  action  of  the  waves  would  tend  to 
chisel  off  and  keep  level  the  upper  surface  of  the  beds,  whether 
accumulations  of  sand  or  earth,  or  of  shells  or  corals.  If  the 
bottom  over  the  region  were  very  slowly  sinking,  the  accumu- 
lations might  go  on  thickening,  and  the  beds  continue  to 
have  the  same  level  or  horizontal  position.  Strata  formed 
along  the  borders  of  rivers  and  lakes  have  horizontal  beds, 
and  so  have  those  on  the  borders  of  the  ocean;  and  for  a 
like  reason,  that  the  water  works  through,  or  with  a  reference 
to,  its  surface,  which  is  horizontal.  Moreover,  the  bottom  of 
tho  border  of  the  Atlantic,  south  of  Long  Island,  is  (see  Fig. 
3,  p.  12),  for  eighty  miles  from  the  coast-line,  so  nearly  hori- 
zontal that  it  deepens  only  1  foot  for  every  600  to  700  ;  and  if 
the  area  were  above  the  ocean,  no  eye  would  detect  that  it 
was  not  perfectly  level. 

Other  beds  were  originally  vast  marshes,  like  the  marshes 
of  the  present  day,  only  larger.     Such  was  the  condition  of 
the  beds  in  the  coal-formation  that  are 
now    coal.      Many    coal-beds    contain 
stumps  of  trees  rising  out  of  the  coal 
(Fig.  39) ;  and  they  always  stand  verti- 
cally on  the  bed,  however  much  the  lat- 
ter may  be  displaced,  showing  that  the 
bed  was  horizontal  when  it  was  formed, 
or  when  the  trees  were  growing. 

Exceptions  to  a  horizontal  position.  —  When  a  river  empties 
into  a  lake  or  sea,  the  bottom  of  which,  near  its  mouth,  is 
more  or  less  inclined,  the  deposits  of  detritus  made  by  the 

Fig.  40. 


Fig.  39. 


river  will  for  a  while  conform  to  the  slope  of  the  bottom, 
as  in  Fig.  40.     When  rivers  fall  down  precipices,  they  make 


52  STRUCTURAL   GEOLOGY. 

a  steep  bank  of  earth  at  the  foot,  whose  layers,  if  any  are 
made,  have  the  slope  of  the  bank.  In  beach-made  deposits 
the  layers  have  the  slope  of  the  beach  (page  44).  But  these 
and  similar  cases  of  exceptions  to  a  horizontal  position  are  of 
small  extent. 

2.  Dislocations  of  strata.  —  Most  of  the  strata  of  the  globe 
have  lost  their  original  horizontal  position  so  as  to  be  more  or 
less  inclined ;  and  some  are  even  vertical.  They  are  occasion- 
ally bent  or  folded,  as  a  quire  of  paper  might  be  folded,  only 
the  folds  are  miles,  or  scores  of  miles,  in  sweep. 

They  have  often  also  been  fractured,  and  the  separated 
parts  have  been  pushed,  or  else  have  fallen,  out  of  their 
former  connections,  so  that  the  portion  of  a  stratum  on  one 
side  of  a  fracture  is  often  inches,  feet,  or  even  miles,  above 
that  on  the  other  side. 

It  is  stated  on  page  1,  that  a  thickness  of  rock  equal  to  18 
or  20  miles  is  open  to  the  geological  explorer.  This  could 
not  be  true  were  all  strata  in  their  original  horizontal  posi- 
tion ;  for  in  that  case  the  most  that  would  be  within  reach 
would  not  exceed  the  height  of  the  highest  mountain.  But 
the  upturning  which  the  earth's  crust  has  undergone  has 
brought  the  edges  of  strata  to  the  surface,  and  there  is  hence 
no  such  limit:  however  deep  stratified  beds  may  extend, 
there  is  no  reason  why  the  whole  should  not  be  brought  up 
so  as  to  be  exposed  to  view  in  some  parts  of  the  earth's 
surface. 

The  following  are  explanations  of  the  terms  used  in  de- 
scribing the  positions  of  strata  :  — 

7.  Outcrop.  —  The  portions  or  ledges  of  strata  projecting 
out  of  the  ground,  or  in  view  at  the  surface  (Fig.  41). 

2.  Dip.  —  The  angle  of  slope  of  inclined  or  tilted  strata. 
In  Figs.  41,  42,  d  p  is  the  direction  of  the  dip.  Both  the 
angle  of  slope  and  the  direction  are  noted  by  the  geologist : 
thus,  it  may  be  said  of  beds,  the  dip  is  50°  to  the  south,  or 
45°  to  the  northwest,  etc. 

When  only  the  edges  of  layers  are  exposed  to  view,  it  is 


DISLOCATIONS  OF  STRATA. 


53 


not  safe  to  take  the  slope  of  the  edges  as  the  slope  of  the 
layers ;  for  in  Fig.  42  the  edges  on  the  faces  1,  2,  3,  4  are 


Fig.  41. 


all  edges  of  the  same  beds,  and   only  those  of  the  face  1 
would  give  the  right  dip. 


The  dip  is  measured  by  means  of  instruments  called  clino- 
meters.    In  Fig.  43,  abed  represents  a  square  block  of 


Fig.  43. 


wood,  having  a  graduated   arc  I  c  and   a   plummet  hung 
below  a.     Placed  on  the  sloping  surface  A  B,  the  position 


54  STRUCTURAL  QEOLOGY. 

of  the  plummet  gives  the  angle  of  dip.  This  kind  of  clino- 
meter is  often  made  in  the  form  of  a  watch  and  combined 
with  a  compass.  It  is  most  convenient  for  use  when  it  has 
a  square  base.  One  like  that  figured  is  easily  made  out  of  a 
piece  of  board ;  it  may  be  3  to  4  inches  on  a  side,  and  half 
an  inch  or  so  thick.  To  avoid  errors  from  the  un evenness  of 
a  rock,  a  board  should  be  laid  down  first  and  the  measure- 
ment be  made  on  its  surface.  But  if  the  instrument  has 
a  square  base  it  is  often  best  to  measure  the  dip  by  holding 
it  between  the  eye  and  the  rock,  with  one  edge  of  the  base  in 
the  direction  of  the  dipping  layers. 

8.  Strike.  —  The  horizontal  direction  at  right  angles  with 
the  dip.  In  Fig.  41,  the  dotted  line  s  t  represents  the  direc- 
tion of  the  strike.  It  is  measured  by  means  of  a  small  com- 
pass which  usually  forms  part  of  the  clinometer.  Such  a 
compass  may  be  set  in  a  clinometer  made  like  the  above 
figure  (Fig.  43).  It  need  not  be  central  in  the  square,  but 
should  have  the  meridian  line  parallel  to  one  of  the  four 
sides.  If  the  edges  of  the  layers  in  view  over  a  ledge  are  in 
any  part  quite  horizontal,  the  direction  of  those  edges  will 
give  the  true  strike ;  but  if  they  are  at  all  inclined,  a  hori- 
zontal line  should  be  drawn,  if  possible,  on  the  surface  of 
one  of  the  layers.  The  clinometer  may  be  used  also  for 
measuring  the  dip  of  rocks  that  are  rods  distant,  and  the 
slopes  of  distant  mountains. 

4.  Fault.  —  In  the  making  of  faults  (aa,  bb,  Fig.  44)  there 

is  first  a  fracturing,  and  then  a 

^     Fig.  44.  shoving  up  or  down  of  the  beds 

on  one  side  of  the  fracture ;  that 
is,  a  downthrow  on  ,one  side  or 
an  upthrow  on  the  other.  The 
amount  of  displacement  is  the 
amount  of  fault ;  it  may  be  a 
foot  or  less,  or  10,000  feet  or  more. 
In  Fig.  17,  on  page  42,  the  vein  a  is  faulted  along  the  line 
of  b.  The  friction  attending  the  downthrow  may  cause  a 


DISLOCATIONS  OF  STRATA. 


55 


bending  of  the  layers  in  contact,  as  along  the  line  bb,  in 
Fig.  44.  The  deepest  fractures  and  faults  have  been  produced 
in  connection  with  the  making  of  mountains. 

5.  Folds  or  flexures.  —  Folds  or  flexures  in  strata  are  repre- 
sented in  the  following  sections ;  Fig.  45,  A,  B,  and  in  the  nat- 


Fig.  45. 


ural  section,  Fig.  46,  from  the  Appalachian  Mountains,  a  region 
of  numerous  flexures  on  a  grand  scale,  as  well  as  of  many  faults ; 
some  flexures  having  a  span  of  several  miles,  and  others  of 
only  a  few  feet  or  inches. 

In  Fig.  45,  ax  is  the  axis  or  axial  plane  of  the  fold. 


Fig.  46. 


The  flexure  very  often  has  one  side  steeper  than  the  other, 
as  illustrated  above.  In  some  regions  the  push  by  which  they 
were  made  wTas  continued  until  the  fold  became  vertical; 
and,  further  still,  until  the  top  was  pressed  over  beyond  the 
vertical,  and  fold  of  this  kind  followed  fold,  as  illustrated  in 
Fig.  47.  In  more  extreme  cases 
the  push  has  continued  until  there 
has  been  produced  a  complete  over- 
turn or  inversion  of  the  beds,  as  is 
represented  in  the  following  section 
(by  Eenevier)  from  the  Alps  east  of  the  Ehone,  the  whole 
height  of  whic>  is  6,500  feet.  The  bed  A,  which  before 
the  folding  was  the  uppermost  stratum  is  folded  back  on 
itself  for  more  than  three  miles;  and  B,  C,  D,  E,  which 


Fig.  47. 


56 


STRUCTURAL  GEOLOGY. 


Section  West  to  East.  —  A,  upper  Eocene;  B, 
Nummulitic  beds,  or  lower  Eocene  ;  C,  D,  E, 
Cretaceous  (E.  Neocoraian);  G,  Jurassic  lime- 
stone ;  H,  Carboniferous  ;  I,  Metamorphic  ; 
M,  Dent  tie  Morcles. 


were  originally  underlying 
strata,  now  overlie  it,  up- 
side down.  It  is  seen 
that  the  strata  C,  D,  E 
are  present  only  in  the 
overturned  part  of  the  fold ; 
these  beds  must  have  cov- 
ered G  to  the  westward  and 
not  to  the  eastward. 

Flexures  often  have  frac- 
tures somewhere  along  the 
bend ;  and  the  fractures  are 
often  lines  of  faults. 

6.  Anticline.  —  An  upward  bend  in  the  strata,  sloping  away 
from  a  common  plane  in  opposite  directions,  as  the  layers 
either  side  of  a.  x  in  Fig.  45  A :  the  axis  is  here  called  an 
anticlinal  axis.     The  word  anticline  is  from  the  Greek  dvrl, 
in  opposite  directions,  and  ic\ivw,  I  incline. 

7.  Syncline.  —  A  downward  bend,  the  strata  sloping  toward 
a  common  plane.     In  Fig.  45  B,  a  x,  a  x  are  anticlinal  axes, 
af  xf,  between  the  others,  a  synclinal  axis.     The  word  syncline 
is  from  the  Greek  avv,  together,  and  /c\ivo). 

8.  Monocline.  —  Having  the  strata  sloping  in  only  one  direc- 
tion, as  when  strata  are  fractured  and  those  of  one  side  are 
lifted  along  the  fracture.     The  word  monocline  is  from  the 
Greek  /JLOVOS,  one,  and  K\LVW. 

9.  Geanticline,  Geosyncline.  —  Bendings  of  the  earth's  crust, 
geanticline  an  upward  bend,  and  geosyncline  a  downward  bend. 
These  words  are  from  the  Greek  for  earth  and  the  words  anti- 
cline and  syncline. 

•In  ordinary  synclines  and  anticlines  the  flexures  are  those 
of  the  strata  which  overlie  the  earth's  crust.  The  bendings 
of  the  earth's  crust  are  necessarily  of  very  small  angle  and 
broad  span,  on  account  of  its  thickness ;  one  of  10°  in  a  crust 
25  miles  thick  with  a  span  of  only  25  miles  is  not  to  be 
looked  for. 


UNCONFORMABLE    STRATA. 


57 


Fig.  49a.         Fig.  49b* 


The  subject  of  flexures  and  faults  is  best  studied  by  mak- 
ing models  out  of  sheets  of  moist  clay  (or  better  of  paraffine 
containing  a  little  beeswax),  using  lampblack  and  red  and 
yellow  ochre  for  coloring  the  different  beds,  and  then  making 
cross-sections. 

10.  Effects  of  denudation  on  Flexed  or  Upturned  Rocks ;  Decapi- 
tated Folds.  —  If  the  top  of  the  fold  in  Fig.  49  a  were  cut  off  at 
a  b,  there  would  remain  the  part 
represented  in  Fig.  49  b,  in  which 
there  is  no  appearance  of  any  fold, 
and  only  a  uniform  series  of  dips; 
and  although  1',  2',  3'  appear  to 
be  the  lower  strata  of  the  series, 
they  are  actually  parts  of  1,  2,  3. 

A  long  series  of  such  folds  pressed  together,  and  then  decapi- 
tated, would  make  a  series  of  uniform  dips  over  a  wide  ex- 
tent of  country,  obscuring  wholly  the  true  stratification. 

This  obscuring  of  the  true  succession  has  been  greatly  in- 
creased by  the  removal  of  the  beds  over  great  areas  and  the 
filling  up  of  intermediate  depressions  by  soil:  so  that  the 

Fig.  50. 


L    2  3    3'2'r 


rocks  are  visible  only  at  long  intervals  (as  in  Fig.  50).    Many 

of  the  difficulties  in  the  study  of  rocks  arise  from  this  cause. 

11.  Unconformable  strata. — When  strata  have  been  tilted, 

or  folded,  and,  subsequently,  horizontal  beds  have  been  laid 


Fig.  51. 


down  over  them,  the  two  sets  are  said  to  be  unconformable 
because  they  do  not  conform  in  dip.  It  is  a  case  of  uncon- 
formability  in  the  stratification.  Tims,  in  Fig.  51  the  beds 


58  STRUCTURAL   GEOLOGY. 

a  b  are  unconformable  to  those  below  them ;  so  also  the  tilted 
beds  c  d  are  unconformable  to  those  beneath,  and  the  beds  e  f 
to  the  beds  c  d. 

It  is  plain  that  the  folded  rocks  represented  in  Fig.  51  are 
the  oldest,  and  that  the  folding  took  place  before  the  overly- 
ing beds  were  deposited.  Again,  it  is  evident  that  the  beds 
below  the  line  c  d  are  older  than  the  beds  between  c  d  and  e  f, 
and  also  that  they  were  tilted  and  faulted  before  the  latter  were 
formed.  Supposing  the  underlying  folded  or  upturned  rocks 
were  those  of  the  Alps  :  if  the  upper  of  them  were  of  the  age  of 
the  Chalk  (the  Cretaceous  period)  and  contained  marine  fossils, 
showing  them  to  be  of  marine  origin,  and  the  unconformably 
overlying  beds  belonged  to  some  division  of  the  Tertiary,  the 
geologist  would  conclude  that  the  upturning,  in  which  the 
mountains  were  lifted  above  the  sea,  occurred  after  the  period 
of  the  Chalk,  and  before  that  to  which  the  Tertiary  beds 
belonged.  Or,  if  the  latest  underlying  marine  beds  were  of 
the  1st  period  of  the  Tertiary,  and  the  overlying  of  the  2nd 
period,  then  the  time  of  uplift  would  be  more  narrowly  de- 
termined as  directly  following  the  first  of  these  periods. 
These  examples  illustrate  the  importance  to  geology  of  obser- 
|  vations  on  unconformability  in  stratification. 

Unconformability  of  overlap  is  a  kind  in  which  there  is 
scarcely  any  appreciable  unconformability  in  dip,  and  no 
upturning  was  concerned.  It  exists  when  the  sea  of  one 
era,  after  depositing  horizontal  beds,  has,  in  the  following 
era,  spread  far  over  the  land  and  has  deposited  another  series 
of  beds  with  these  new  limits.  These  changes  of  sea-level 
were  going  forward  during  the  progress  of  most  formations, 
and,  consequently,  unconformability  through  overlap  should 
be  common,  though  not  always  easily  distinguished. 

3.    Order  of  Arrangement  of  Strata. 

It  has  been  explained  that  the  strata  are  historical  records 
as  to  the  past  conditions  of  the  earth's  surface.  In  order 


EQUIVALENCY  OF  ROCKS.  59 

that  the  records  may  make  an  intelligible  history,  there 
must  be  some  way  of  arranging  them  in  their  proper  order, 
that  is,  in  the  order  of  time.  The  determination  of  this  order 
is  one  of  the  first  things  before  the  geologist  in  his  exam- 
inations of  a  country. 

Many  difficulties  are  encountered. 

1.  The  strata  of  the  same  period  or  time  —  called  equiva- 
lent strata,  because  approximately  equivalent  in  age  —  differ, 
even   on  the   same  continent.     Sandstones  and  shales  were 
often  forming  along  the  Appalachians  in  Pennsylvania  and 
Virginia,  when  limestones  were  in  progress  over  the  Missis- 
sippi Valley.    The  chalk-formation  in  England  contains  thick 
strata  of  chalk ;  but  in  Eastern  North  America  the  same  for- 
mation exists  without  any  chalk. 

2.  When  rocks  have  been   forming  in  one   region,  there 
have  been  none  in  progress  in  many  others.     Hence  the  series 
of  strata  serving  as  records  of  geological  events  is  nowhere 
perfect.     In  one  country  one  part  may  be  very  complete ;  in 
another,  another  part ;  and  all  have  their  long  blanks, —  that 
is,  large  parts  of  the  series  entirely  wanting.     In  New  York 
and  the  States  west  to  the  Mississippi,  there  is  only  part  of 
the  lower  half  of  the  series.  In  New  Jersey  there  is  part  of 
the  lower  half  and  part  of  the  upper  half,  with  wide  breaks 
between.     Over  a  large  part  of  Northern  New  York  there 
exist  only  the  very  earliest  of  rocks. 

The  thickness  of  the  fossiliferous  series  in  the  State  of 
New  York,  south  of  its  centre,  is  about  13,000  feet,  and  north 
of  its  centre  they  thin  out  to  a  few  feet ;  in  Pennsylvania, 
the  thickness  is  about  30,000  feet  (Lesley) ;  in  Indiana  and 
other  adjoining  States  west  and  south,  3,500  to  6,000  feet. 
In  Great  Britain,  the  whole  thickness  above  the  unfossiliferous 
bottom-rocks  is  over  100,000  feet. 

3.  The  rocks  of  a  country  are  to  a  great  extent  covered 
with  earth  or  soil,  so  that  they  can  be  examined  only  at  dis- 
tant points. 

4.  The    strata,  in    many    regions,    have    been    displaced, 


60  STRUCTURAL  GEOLOGY. 

folded,  fractured,  faulted,  and  even  crystallized  extensively, 
adding  greatly  to  the  difficulties  in  the  way  of  the  geological 
explorer. 

The  following  are  the  methods  to  be  used  in  determining 
the  true  order  of  arrangement :  — 

A.  In  sections  of  the  rocks  exposed  to  view  in  the  sides 
of  valleys   or  ridges,  the  order  should  be  directly  studied, 
and  each  stratum  traced,  as  far  as  possible,  through  all  the 
exposed  sections. 

When,  through  large  intervals,  a  covering  of  soil  or  water 
prevents  the  tracing  of  the  beds,  other  means  must  be  used. 

B.  The  aspect  or  composition   of    the   rock  may  help  to 
determine   which   strata   are   identical.      But   this    method 
should  be  used  with  great  caution,  for  the  reason   stated 
above,  in  §  1, —  that  rocks  made  at  the  very  same  time  may  be 
widely  different ;  and,  conversely,  those  made  in  very  differ- 
ent periods  may  look  precisely  alike  in  color  and  texture. 

C.  Fossils  afford  the  best  means  of  determining  identity. 
This  is  so  because  of  the  fact,  already  mentioned,  that  the 
fossils  of  an  epoch  are  very  similar  in  genera  —  if  not  also 
in  species  —  the  world  over ;  and  those  of  different  epochs 
are  different  in  these  respects.     The  geologist,  by  studying 
the  fossils  of  the  several  beds  at  any  locality,  learns  which 
kinds  are  characteristic  of  each  bed,  and  the  order  of  succes- 
sion.    Then,  by  comparing  the  beds  of  different  localities,  he 
ascertains  whether  any  are  essentially  alike  in  species,  and 
therefore  of  like  age  or  period,  and  from  this  determination 
continues  further  his  study  of  the  order  of  succession.     By 
pursuing  this  course,  for  all  accessible  localities  over  a  coun- 
try, and  different  countries,  geologists  have  ascertained  the 
characteristic  kinds  of  fossils  for  the  successive  strata  through 
the  long  series  of  formations ;  and  the  lists  which  have  been 
thus  made  serve  for  the  identification  of  strata  in  widely  dis- 
tant regions.     By  a  comparison  of  fossils  it  was  proved  that 
the  chalk-formation  exists   in    Eastern   North   America,  al- 
though there  is  no  chalk  to  be  found  there.     In  the  same 


EQUIVALENCY   OF  KOCKS.  61 

manner,  the  equivalents  in  America  of  the  principal  subdivi- 
sions of  the  rock  series  of  Britain  and  Europe,  Asia,  and  even 
Australia,  are  approximately  ascertained ;  for  this  means  of 
determination  is  a  universal  one,  applying  to  the  equivalency 
of  rocks  in  different  hemispheres  as  well  as  those  on  the  same 
continent. 

This  method  has  its  doubts.  These  doubts  arise  (1)  from  the 
fact  that  one  continent  may  have  received  part  of  its  species 
from  another  long  after  their  first  appearance  on  that  other ; 
and,  (2)  from  another  fact,  that  the  exterminations  of  species 
which  have  taken  place  at  the  close  of  a  period  may  have 
been  far  more  complete  in  one  region  than  another,  so  that 
certain  species  were  living  long  in  one  after  their  disappear- 
ance from  the  other.  Again,  there  are  doubts  arising  (3)  from 
the  fact  that,  in  any  period,  the  life  of  one  locality  is  very  dif- 
ferent from  that  of  another,  on  account  of  differences  in  purity 
of  waters,  muddy  or  rocky  bottom,  and  temperature.  The 
removal  of  all  doubts,  especially  with  respect  to  the  minor 
subdivisions  of  the  geological  series  on  different  continents, 
or  distant  parts  of  the  same  continent,  is  not  to  be  looked 
for.  Yet,  by  proceeding  with  care,  and  using  not  isolated 
facts,  but  the  whole  range  afforded  by  the  fossils,  animal  as 
well  as  vegetable,  the  general  order  of  succession  may  be 
made  out  for  each  country,  if  not  the  precise  parallelism  for 
different  countries. 


PART  III. 

DYNAMICAL  GEOLOGY. 


DYNAMICAL  GEOLOGY  treats  of  the  causes  or  origin  of 
events  in  geological  history,  —  that  is,  of  the  origin  of  rocks, 
of  disturbances  of  the  earth's  strata  and  the  accompanying 
effects,  of  valleys,  of  mountains,  of  continents,  and  of  the 
changes  in  the  earth's  features,  climates,  and  living  species. 
The  agencies  of  most  importance,  next  to.  the  universal 
power  of  Gravitation  and  Cohesive  and  Chemical  attraction, 
are  Life,  the  Atmosphere,  Water,  and  Heat. 

The  following  are  the  subdivisions  of  the  subject  here 
adopted:  1.  Life;  2.  The  Chemical  action  of  the  Atmosphere 
and  Waters;  3.  Mechanical  effects  of  the  Atmosphere;  4.  Me- 
chanical effects  of  Water ;  5.  Action  of  Heat ;  6.  Movements 
in  the  earths  crust,  and  their  consequences,  including  the  fold- 
ing and  uplifting  of  strata,  and  the  origin  of  mountains 
and  of  the  earth's  general  features. 

I.  -  LIFE. 
A.    Formative  Effects. 

Life  has  done  much  geological  work  by  contributing  mate- 
rial for  the  making  of  rocks.  Nearly  all  the  limestones  of 
the  globe,  all  the  coal,  and  some  siliceous  beds,  besides  por- 


ORGANIC   MATERIALS  OF  ROCKS. 


63 


tions  of  rocks  of  other  kinds,  have  been  formed  out  of  the 
stony  relics  of  living  species.  Both  animals  and  plants  have 
been  large  sources  of  the  material.  The  skeletons  or  stony 
secretions  of  animals,  after  f ulrilling  the  purposes  of  life,  have 
been  turned  over  to  the  mineral  kingdom,  to  be  made  into 
minerals  and  rocks.  Similarly,  from  vegetable  structures 
have  come  beds  of  stone  as  well  as  beds  of  coaL 


1.  KINDS  AND  SOURCES  OF  ORGANIC  MATERIALS. 

A.  Calcareous  material,  or  that  of  which  limestones  consist, 
has  been  derived  chiefly  from  the  following  sources. 

1.  SHELLS  OF  MOLLUSKS.  —  These  include : 

(1.)  The  ordinary  bivalve  shells,  like  the  oyster  and  clam 
(described  on  page  182  as  Lamellibranch  Mollusks). 

Figs.  52-59,   BBACHIOPOD    MOLLUSKS. 


BRACHIOPODS.—  Fig.  52,  Waldheimia  flavescens,  interior  view  ;  53,  loop  of  Tere- 
bratula  vitrea ;  54,  id.  Terebratulina  caput-serpentis  ;  55,  Spirifer  striatus  ;  56,  same, 
interior  of  dorsal  valve ;  57,  Atliyris  concentrica ;  58,  59,  Atrypa  reticularis,  the  latter 
dorsal  valve. 

(2.)  Other  bivalve  shells  (those  of  Brachiopod  Mollusks) 
having  symmetrical  forms,  as  illustrated  in  Figs.  52  to 
59.  Figs.  52,  56,  59  show  the  characters  of  the  interior  of 


64 


DYNAMICAL   GEOLOGY. 


the  shells.     In  ancient  time  the  shells  of  this  tribe  exceeded 
all  others  in  abundance,  but  now  they  are  relatively  few. 

(3.)  The  univalves  (shells  of  Gasteropod  Mollusks),  having 
commonly  spiral  forms :  like  the  snail  and  the  kinds  repre- 
sented in  Figs.  GO  to  65. 


Figs.  60-65. 


Figs.  66,  67,  CORALS. 


GASTEROPODS.  —  Fig.  60,  Pyrifusus  Newberryi;  61,  62,  Bulla  speciosa;63,  An- 
clmra  (Drepanoclieilus)  Americana  ;  64,  Fasciolaria  buccinoides  ;  65,  Margarita  Nebra-S' 
censis. 

(4.)  Other  species  (Cephalopods)  some  of  which  are  repre- 
sented in  Figs.  347-351,  on  page  298.  Besides  these  there 
are  still  others  (Bryozoans)  which  make  small  coral-like 
and  encrusting  forms,  illustrated  on  page  181. 

2.  CORALS  (Figs.  66, 
67).  —  The  stony  secre- 
tions, mainly  of  Polyps. 
They  contributed  large- 
ly to  the  older  rocks  of 
the  world  and  are  still 
making  great  lime- 
stone formations.  Fi<? 


66  represents  a  living 
coral,  and  67,  a  fossil 
species. 

There  are   also  Millepore  or  Hydroid  Corals  (page  184) 
among  the  limestone-making  species. 


ORGANIC   MATERIALS  OF  ROCKS. 


65 


3.  CRINOIDS. —  Species   of 
Echinoderms  (page  184)  hav- 
ing   radiating    arms    above, 
about    the    mouth,    and    a 
stem  usually,  for  attachment, 
the  whole  made  of  small  cal- 
careous pieces.     Some  lime- 
stones  were   formed   chiefly 
from    remains    of    Crinoids. 
Of  the  three  figures   given, 
68  represents  an  ancient  kind 
(reduced),  and  70  is  a  living 
Atlantic      species      (natural 
size),  from  Wy  ville  Thomson' s 
"  Depths    of    the   Sea,"  — a 
kind  that  plants  itself  in  the 
mud   of   the   sea-bottom   by 
means  of  the  appendages  at 
the  base  of  the  stem,  instead 
of  being  firmly  attached  or 
rooted.    Fig.  69  represents  a 
portion  of  a  mass  of  ancient 
limestone  made  up  of  frag- 
ments of  the  stems  of  crin- 
oids.     The  few  existing  spe- 
cies   occur     in     the     ocean 
at   various   depths   to    2435 
fathoms,  but  are  most  com- 
mon  between    80    and    400 
fathoms. 

4.  FORAMINIFERS    OR    CAL- 
CAREOUS   SHELLS    OF    EHIZO- 

PODS. —  These  shells  (Figs. 
71-84)  are  mostly  very  small, 
and  yet  through  their  abun- 
dance they  have  been  very  im- 


Figs.  68-70, 


CRINOIDS :  Fig.  68,  Apiocrinus  Roys- 
sianus  (a ,  lower  part  of  stem ) ;  69,  portion 
of  a  mass  of  prinoidal  limestone  ;  70,  Pen- 
tacrinus  Wyville-Thomsom. 


66 


DYNAMICAL    GEOLOGY. 


portant  in  limestone-making.  In  size  they  are  generally 
between  a  grain  of  sand,  and  an  eighth  of  an  inch ;  but  Figs. 
83  and  84  are  of  natural  size,  and  still  larger  occur.  They 
are  all  marine,  the  fresh-water  species  not  having  calcareous 


Pigs.  71-84,  FORAMINIFERS,  OR  SHELLS  OF  RHIZOPODS. 


Fig.  71  Orbnlina  universa  •  72,  Globigerina  rubra  ;  73,  Textilaria  globulosa,  Ehr. ;  74,  Rotalia 
globulosa  ;  74  a,  Side-view  of  Rotalia  Boucuna ;  7.r>,  Grammostomum  phyllodes  Ehr.  ; 
76,  Frondicularia  annularis  ;  77,  Triloculina  Josephiiia  ;  78,  Nodosaria  vulgaris  ;  79,  Lit- 
uola  nautiloides ;  80  a,  Flabellina  rugosa  •  81,  Chrysalidina  gradata :  82  a,  Cuneolina 
Pavonia  :  83,  Nummulites  nuinmularia  :  84  a,  b,  Fusulina  cyliudrica. 

shells.  Some  kinds  belong  especially  to  the  border  region  of 
the  ocean  (Textilarias,  Rotularias,  Nodosarias,  etc.),  while 
others  (Globiyerinas,  Fig.  72  etc.,  and  Fig.  171,  page  185)  be- 
long to  the  open  sea,  or  are  pelagic  kinds.  The  latter  often 
make  the  fine  mud  or  ooze  of  the „ sea-bottom  in  latitudes 
inside  of  60°,  constituting  what  is  called  the  Globigerina 
ooze.  The  chalk  was  made  mainly  of  such  materials. 

5.  SOME  MARINE  PLANTS,  as  (1)  the  Nullipores,  which  look 
like  corals  but  have  no  cells  —  whence  the  name  signifying 
no  pores ;  (2)  the  Corallines,  which  are  delicate,  semi-calcare- 
ous sea-plants ;  (3)  Ooccolitks,  minute  stony  disks  of  a  one- 
celled  sea-plant  (named  from  KOK/COS,  seed),  and  the  related 
Rhabdolitlis  which  are  rod-like  in  shape. 

B.  Siliceous  material  of  organic  origin  is  far  less  abundant 
than  calcareous ;  for  quartz  is  mostly  from  mineral  sources. 


ORGANIC  CONTRIBUTIONS  TO  ROCKS. 


67 


Figs.  85-87,  RADIOLABIANS. 


1.  ANIMAL  IN  ORIGIN.  —  (1.)  Many  Sponges  afford  siliceous 
spicules.     The  forms  of  some  of  the  spicules  are  shown  in 
Figs.  250,  251,  on  page  234,  and  their  fragments,  among  the 
Diatoms  in  the  figure  on  page  68.      The  horny  fibres  which 
make  up  a  sponge  constitute  the  skeleton  of  a  multitudinous 
group  ot  minute  sponge-animals  which  are  somewhat  related 
to  the  Khizopods,     The  spicules,  when  present,  occur  within 
these  fibres  and  often  bristle  their  surface.     (In  some  sponges 
they  are  calcareous.)     Other  sponges,  like  that  of  Fig.  374, 
page  314,  have  the  whole   skeleton  of    silica;    and  these, 
which  are   called  (/lass  or  vitreous  sponges,  grow  over  the 
ocean's  bottom  at  various  depths,  but  most  abundantly  be- 
tween 90  and  100  fathoms. 

(2.)  The  Eadiolarians  (Figs.  85-87)  are  marine  Khizopods 
having  siliceous  shells 
(often  lacework-like), 
which  are  usually  sym- 
metrical about  the  centre 
or  central  line,  and  some- 
times spherical.  The 
name  is  from  the  Latin 
for  radial.  Another  kind 
is  represented  on  page 

186.  They  live  in  all  zones.  The  Challenger  expedition  found 
a  "Radiolarian  ooze"  at  depths  between  11,000  and  23,000 
feet. 

2.  VEGETABLE  IN  ORIGIN. —  Minute  plants,  called  Diatoms 
(from  two  Greek  words  referring  to  a  subdivision  which  takes 
place  in   the  process  of  reproduction),  have  siliceous  shells. 
Some  kinds  are  represented  (part  of  them  broken)  in  Fig. 
88 ;  they  are  from  an  earthy  deposit  near  Richmond  in  Vir- 
ginia.     They   grow   so  abundantly  in  both  fresh  and    salt 
waters  that  they  make  thick  chalk-like  deposits,  and  those 
of  the  deep  ocean,  between  6,000  and  12,000  feet,  are  very 
extensive.     They  live  near  the  surface,  and  in  certain  parts  of 
the  ocean,  the   Polar    seas   included,   they    often    tint    the 


68 


DYNAMICAL  GEOLOGY. 


Fig.  88,  DIATOMS. 


water,  and  are  sometimes  massed  together,  they  are  so 
abundant.  Many  sea-animals  live  on  them.  The  flint,  chert 
and  jasper,  which  form  nodules  and  sometimes  layers  in  lime- 
stone and  other  rocks,  have  been 
made  largely  from  spicules  of 
Sponges,  or  the  shells  of  Eadi- 
olarians  or  Diatoms. 

C.  Phosphatic  material,  chief- 
ly Calcium  phosphate.  —  Ver- 
tebrate animals  (Fishes,  Am- 
phibians, Eeptiles,  Birds,  and 
Mammals  or  Quadrupeds)  have 
contributed  very  little  calcare- 
ous material  to  the  rocks,  com- 
pared with  inferior  tribes  of  ani- 
mals. But  they  have  been  an 
important  source  of  phosphate 
salts,  and  the  deposits  are  often 
worked  because  the  material 
Bones,  scales,  and,  to  some  extent, 
all  animal  tissues  of  vertebrates  and  invertebrates  contain 
phosphatic  material.  The  mineral  apatite,  common  in  many 
crystalline  limestones,  is  a  calcium  phosphate,  and  has  some- 
times had  this  source.  Guano,  which  owes  its  value  largely 
to  its  phosphates,  has  been  made  chiefly  from  the  excrements 
of  birds  in  dry  regions  where  the  birds  long  had  undisturbed 
possession ;  as  on  some  small  coral  islands  in  the  Central 
Pacific,  islands  off  the  Peruvian  coast,  the  coast  of  equatorial 
Africa,  and  in  the  Caribbean  Sea. 

Coprolites,  or  isolated  excrements  of  reptiles  and  fishes,  and 
sometimes  of  other  animals,  occur  in  many  rocks.  Vegetable 
tissues  also  afford  phosphates,  100  parts  of  the  ashes  of  ordi- 
nary meadow  grass  affording  8  parts  of  phosphoric  acid ;  of 
rye-straw,  4  parts;  of  clover,  18  parts;  oc  seaweeds,  1  to  5 
parts. 

The  shells  of  certain  Brachiopods  —  the  Lingnla  and  some 


is  valuable  as  a  fertilizer. 


ORGANIC  CONTRIBUTIONS  TO  ROCKS.  69 

related  species  —  are  largely  phosphatic.  These  shells  and 
the  shells  of  Crustaceans  when  fossilized  are  usually  black, 
because  of  the  large  amount  of  animal  matter  they  contain, 
this  portion  becoming  carbonized. 

D.  Carbonaceous  material.  —  The  most  abundant  contribu- 
tions from  the  vegetable  kingdom  to  rocks  are  the  beds  of 
mineral  coal,  coal  being  made  from  woody  tissues.     Mineral 
oil  has  in  part  the  same  source,  and  partly  is  of  animal  origin. 
Graphite,  which  is  pure  carbon,  is  often  also  of    vegetable 
origin,  coal  sometimes  occurring  changed  to  graphite  when 
it  has  been  subjected  to  high  heat  under  pressure.     Carbona- 
ceous matters,  of  vegetable  or  animal  origin,  give  the  black 
color  to  black  limestones  and  most  shales,  as  is  proved  by 
the  fact  that  when  such  rocks  are  burnt  they  become  white, 
owing  to  the  combustion  of  the  carbonaceous  part.    Diamonds 
have  probably  been  formed  from  the  carbonaceous  materials 
of  a  shale,  by  long  subjection  to  heat  and  moisture,  under 
peculiar  conditions  yet  unexplained. 

E.  Aquatic  species  the  largest  rock-makers  —  The  kinds  of 
life  which  have  contributed  most  material  to  the  earth's  rock- 
formations,  and  which  are  most  common  as  fossils,  are  the 
aquatic,  and  particularly  the  marine.     This  is  so  because  (1) 
the  accumulation  of  material  making  beds  of  rock  has  been 
done  mostly  by  the  sea ;  because  (2)  the  species  which  have 
the  most  stony  matter  in  the  structures,  viz.  corals,  crinoirls 
and  shells  are,  with  small  exceptions,  under  the  last  division, 
aquatic,  and  nearly  all  are  marine;  because  (3)  the  animal 
remains  which  are  in  the  water  readily  become  buried  by 
new  depositions  of   clay  or  sand   through  the  currents  or 
waves,  and   thus   have   a   protection   from   destruction   not 
afforded  to  any  extent  to  species  of  the  land ;  because  (4)  the 
water  and  this  kind  of  burial  also  serve  often  as  a  preventive 
of  complete  decay.      Coal  has  been  made  only  where  the 
plants  grew  in  or  near  marshes  or  shallow  lakes,  or  were 
drifted  into  bays  or  lakes  ;  for  the  leaves  that  fall  in  the  dry 
woods  undergo  complete  decomposition,  and  pass  away  in 


70  DYNAMICAL  GEOLOGY. 

gaseous  combinations.  The  bones  of  animals  dropped  over 
the  land  disappear  by  becoming  the  food  of  other  animals  as 
well  as  by  decay;  while  those  living  about  the  shores  of 
lakes  have  often  become  buried  in  lacustrine  deposits  of  clay 
or  finer  earth,  and  thus  have  had  their  bones  preserved.  Mas- 
todons have  been  mired  in  marshes  and  their  skeletons  pre- 
served whole,  while  the  thousands  that  died  over  the  dry  land 
left  no  relics. 

F.  Fossilization.  —  Shells,  bones,  corals,  etc.,  after  f  ossiliza- 
tion,  have  rarely  their  original  composition.  They  have  in 
almost  all  cases  lost  at  least  the  animal  matter  they  con- 
tained; frequently  they  are  changed  to  quartz,  sometimes 
to  pyrite,  oxide  of  iron,  or  dolomite,  and  occasionally  to  an 
ore  of  copper,  or  to  a  silicate  of  some  kind.  Wood  is  often 
changed  to  quartz  or  to  limestone. 

2.   GEOGRAPHICAL  DISTRIBUTION  OF  MARINE  LIFE. 

The  distribution  of  species  is  an  important  subject  to  the 
geologist,  but  especially  that  of  marine  species,  since  the 
stratified  rocks  and  their  fossils  are  very  largely  of  marine 
origin. 

1.  General  Distribution  in  the  Ocean.  —  Eecent  investigations 
have  shown  that  living  species  not  only  inhabit  the  bordei 
regions  of  the  oceans,  but  also  extend  widely  and  abundantly 
over  a  large  part  of  the  ocean's  depths.     Fishes,  Crabs  and 
other  Crustaceans,  Sea-worms,  Echini,  Star-fishes,  Crinoids, 
Corals,  are  abundant  to  depths  of  10,000  to  13,000  feet,  and 
some  of   them  to   18,000    feet.      Crustaceans    of  large   size, 
allied  to  shrimps,  many  of  them  with  good  eyes,  have  been 
found  at  all  depths  to  2,900  fathoms  ;  and  large  crabs,  with 
perfect  eyes,  at  1,700    fathoms.     Some  species  have  a  very 
wide  range  in  depth ;  one  Coral  (a  disk-shaped  kind,  Bathy- 
actis  symmetrica)  occurs  (states  Moseley)  at  depths  from  30 
to  2,900  fathoms. 

2.  Character  of  the  Sea-bottom.  —  The  material  of  the  ocean's 


DISTRIBUTION  OF   MARINE   LIFE.  71 

bottom  is  generally  a  fine  grayish  mud  or  ooze.  But  over 
vast  regions  above  13,000  feet  in  depth  occurs  the  Globigerina 
ooze,  and  at  these  and  greater  depths  other  areas  of  Diatom 
ooze,  and  smaller  of  Radiolarian  ooze. 

The  character  of  the  bottom  shows  that  sediments  from  the 
rivers  of  the  continents  are  not  carried  far  out  to  sea.  Stones 
of  a  pound  weight,  and  larger,  occur  100  miles  southeast  of 
Long  Island ;  but  these  are  supposed  by  Verrill  to  have  been 
carried  out  by  shore  ice.  Clay  with  some  fine  quartz  sand 
and  particles  of  mica  make  up  the  gray  ooze  ;  and  the  winds 
may  be  a  principal  source  of  the  sand  and  mica.  Pumice 
and  fine  materials  of  volcanic  origin  are  also  widely  distrib- 
uted, indicating  that  the  driftings  by  the  winds  from  volcanic 
islands  have  been  to  great  distances  and  over  very  large  areas. 
The  ooze  has  often  a  reddish  color,  which  is  attributed  to  the 
oxidation  of  the  iron  of  the  pyroxene  or  hornblende  in  vol- 
canic cinders ;  and  grains  and  nodules  of  oxide  of  manganese, 
probably  from  the  same  source,  are  very  common  over  the 
ocean's  bottom. 

The  bottom  is  the  receiving  place  of  all  the  dead  remains 
of  the  ocean's  life,  both  plant  and  animal,  exclusive  of  the 
very  large  part  that  does  not  have  a  chance  to  reach  the  bot- 
tom, because  of  the  eaters.  In  the  Challenger  expedition,  the 
dredge,  in  one  region,  brought  up  a  hundred  or  more  shark's 
teeth,  and  between  30  and  40  ear-bones  of  Cetaceans  or  ani- 
mals of  the  whale  tribe.  Among  the  shark's  teeth,  one  was 
four  inches  wide  at  base,  and  apparently  an  Eocene  tooth  ;  and 
its  being  buried  not  more  than  a  foot,  although  lying  there 
since  the  early  Tertiary,  is  regarded  as  evidence  of  the  very 
small  amount  of  detritus  that  falls  over  the  bottom. 

3.  Causes  limiting  Distribution.  —  The  two  prominent  physi- 
cal causes  limiting  distribution  are  the  amount  of  (1)  heat, 
and  (2)  light. 

a.  Temperature.  — The  temperature  of  the  waters  varies  (1) 
with  the  zones,  from  90°  F.  in  the  tropics  to  32°  F.,  and  even 
28°  F.,  in  the  polar  seas ;  (2)  with  the  distribution  of  marine 


72  DYNAMICAL  GEOLOGY. 

currents,  the  warm  currents  from  the  equatorial  regions,  and 
the  cold  from  high  latitudes ;  (3)  with  the  depth,  the  temper- 
ature diminishing  downward  to  35°  F.  as  a  general  thing,  but 
in  some  places  to  28°  in  the  polar  regions  and  polar  currents. 
In  depth,  there  is  in  the  tropics  a  temperature  of  45°,  and 
often  of  40°,  within  300  fathoms  of  the  surface,  and  almost 
everywhere  of  40°  and  less,  below  1,000  fathoms;  so  that 
from  1,000  fathoms  to  the  greatest  depths,  the  variation  is 
only  from  40°  to  32°  F.,  or  in  extreme  cases  to  28°  F. 

The  influence  of  marine  currents  on  the  temperature  is 
great.  The  Gulf  stream,  a  deep  Atlantic  current,  carries  heat 
from  the  tropical  to  the  polar  seas.  The  portion  of  the  broad 
current  which  passes  through  the  Florida  Straits  is  as  deep 
as  the  Straits,  400  fathoms,  and  83°  to  44°  F.  in  temperature, 
and  has  a  maximum  velocity  of  5  miles  an  hour.  It  washes 
the  deep-water  border  of  the  Atlantic  basin  at  depths  between 
60  and  300  fathoms  off  Charleston,  and  between  60  and  150 
fathoms  (Verrill)  southeast  of  New  England ;  crosses  the 
ocean  northeastward  to  British  seas,  has  a  temperature  of  45° 
off  the  Faroe  Islands  at  a  depth  of  600  to  800  fathoms ;  and 
thence  continues  on  pole- ward.  From  the  polar  regions  the 
waters,  chilled  down  to  39°-28°  F.,  flow  back,  as  the  "  Labra- 
dor current"  along  the  east  coast  of  America,  and  also  south- 
ward beneath  the  warmer  current  over  the  ocean's  depths 
to  the  equator  and  beyond.  Comparatively  little  goes  out 
through  Behrings  Straits,  because  the  depth  is  only  150  feet. 

In  the  Pacific,  there  is  a  warm  or  tropical  current  on  the 
west  side,  answering  to  the  Gulf  Stream  of  the  Atlantic. 
Again,  on  the  east  side  of  the  South  Pacific,  a  reverse  flow 
exists :  a  cold-water  current  from  the  southwest  strikes  the 
submarine  slopes  of  southern  South  America,  and  carries  cold 
to  the  equator,  and  thus  narrows  the  region  of  tropical 
waters. 

b.  Limiting  range  of  Temperature  for  Species.  — The  range 
of  temperature  favorable  to  any  marine  species  is  small  — 
generally  not  over  20°  R,  and  often  less  than  15°  F.  Within 


DISTRIBUTION   OF   MARINE  LIFE.  73 

the  favorable  temperature  the  species  thrive ;  approaching  the 
limit,  the  size  usually  diminishes  ;  and  beyond  it,  growth  and 
egg-development  cease.  A  current  too  cold  for  species  within 
its  reach  is  destructive,  even  more  so  than  one  of  too  much 
warmth.  The  enlarging  of  the  polar  current  by  an  increase 
of  high-latitude  cold,  as  in  a  glacial  era,  might  destroy  the 
sea- bolder  life  of  the  oceans  nearly  to  the  equator. 

Co  Light.  —  Light  is  the  chief  limiting  cause  as  to  depth 
(Fuchs).  If  it  were  temperature,  multitudes  of  species  might 
grow  hundreds  of  feet  below  their  present  level..  Light  has 
been  found  by  experiment  to  penetrate  downward  in  the 
ocean  43  to  50  fathoms ;  arid  what  passes  this  limit  is 
very  feeble  in  amount.  The  species  of  depths  less  than  40 
fathoms  differ  to  a  large  extent  from  the  deep-sea  species, 
or  those  below  this  limit ;  they  are  (as  stated  by  Fuchs)  the 
species  of  the  light,  the  latter  the  species  of  the  darkness.  The 
two  ranges  of  species,  the  ocean-border  (or  species  of  the 
light)  and  the  deep-sea  species  (or  those  of  the  darkness)  are 
mingled  somewhat  between  depths  of  30  and  90  fathoms,  and 
some  shore  species  extend  down  to  a  much  greater  depth. 

The  eyes  of  animals  of  the  deep  or  dark  sea-depths  are  often 
blind,  or  else  unusually  large.  The  blindness  is  evidence  of 
darkness,  and  the  large  eyes,  of  adaptation  to  the  very  feeble 
light  of  the  regions.  Env  this  feeble  light  may  be,  as  Dr. 
Carpenter,  Wyville  Thomson  and  others  have  supposed,  that 
of  phosphorescence ;  lor  many  Crustaceans,  Alcyonia,  Star- 
fishes, and  other  kinds  are  brightly  phosphorescent.1 

4.  The  Border  Region,  or  that  of  the  Animals  of  the  Light. 
Over  the  ocean's  border  region  not  only  is  the  diversity  of 
temperature  between  the  equator  and  the  poles  felt  in  full 

1  The  following  are  enumerated  as  the  most  characteristic  types  of  the 
dark  sea-depths.  Of  Corals,  Oculinidse,  Cryptohelia  and  various  solitary 
species  ;  the  Vitreous  Sponges  ;  Crinoids  (Pentacrinus,  Rhizocrinus,  Hyo- 
crinus,  Bathycrinus)  ;  of  Echinoids,  Echinothimse,  Pourtalesire,  Ananchytidse  ; 
of  Asterioids,  Brisinga  ;  Holotlmriae  of  sub-order  Elasmopodia  ;  and  Fishes, 
ribbon -like  in  form,  of  the  families  Lepidopidse,  Trachypteridse,  Macruridse 
and  Ophidiidae. 


74  DYNAMICAL  GEOLOGY. 

force,  but  also  that  produced  by  the  encroaching  warm  and 
cold  currents.  Off  Eastern  North  America  down  to  Cape 
Hatteras,  the  cold  Labrador  current  cools  the  waters  over 
the  border  region  between  the  Gulf  Stream,  in  65  fathoms, 
and  the  shore  line ;  while  south  of  this  cape  the  Gulf  Stream 
has  possession. 

The  other  causes  limiting  distribution  in  the  border  regions 
of  the  ocean  are:  (1)  the  condition  of  the  water,  whether 
pure,  or  on  the  other  hand,  impure  from  sediments  and  fresh 
waters  received  from  the  land ;  (2)  the  character  of  the  lottom, 
whether  of  mud,  sand,  or  rock,  and  whether  firm,  or  easily 
stirred  and  made  impure  by  waves  or  currents. 

Reef-forming  Corals  grow  only  in  the  sea-border  regions  of 
tropical  seas,  and  at  shallow  depths.  They  extend  from  the 
equator  to  about  latitude  28°,  where  the  sea-temperature  of 
the  coldest  month  is  not  below  68°  F.  Owing  to  the  warm 
Gulf  Stream,  they  occur  in  the  Atlantic  in  34°  north  latitude, 
the  Bermudas  being  of  coral  formation ;  and  owing  to  the  cold 
waters  off  western  South  America,  they  are  excluded  from 
that  coast  south  of  Guayaquil.  In  depth  the  limit  is  18  ta 
20  fathoms.  A  vast  variety  of  tropical  species  live  and  find 
shelter  among  coral  reefs. 

Sea-weeds,  like  other  plants,  are  species  of  the  light ;  they 
grow  mostly  within  10  fathoms  of  the  surface,  and  rarely 
beyond  30. 

In  the  sea-depths,  or  the  region  of  darkness,  the  range  of 
temperature  is  for  the  most  part  small —  55°  to  30°.  Only 
two  well-marked  divisions  exist :  that  of  the  cold  depths,  the 
temperature  below  45°  F. ;  and  that  within  the  range  of  the 
tropical  currents  (as  the  Gulf  Stream  in  the  North  Atlantic), 
the  temperature  mostly  45°  to  55°  F. 

The  border  of  the  oceanic  basin  where  swept  by  the  Gulf 
Stream  (page  72),  both  on  its  west  side  and  in  the  British 
seas,  is  crowded  with  life,  —  species  of  Crustaceans,  Echino- 
derms,  Polyps,  Mollusks,  Worms,  Fishes  ;  and  some  kinds 
are  larger  than  any  of  the  same  groups  found  in  shallower 


PEAT-FORMATIONS.  75 

waters.  Wyville  Thomson  mentions  his  bringing  up  20,000 
of  one  species  of  sea-urchin  at  one  haul ;  and  Verrill  and 
Agassiz  state  parallel  facts  from  the  American  seas. 

The  life  from  the  cold  and  warmer  regions  differs  to  a  great 
extent  in  species  ;  and  yet  the  groups  represented  in  the  two 
are  largely  the  same.  The  colder  depths  are  much  less  pro- 
fuse in  life,  fail  of  some  prominent  groups,  and  contain  many 
of  very  peculiar  characters. 

The  cold  and  warm  currents  are  in  places  in  abrupt  con- 
tact. The  pushing  of  the  former,  along  the  eastern  ocean- 
border  of  North  America,  over  the  narrow  warmer  area  by 
westerly  winds  was  probably  the  cause  of  the  destruction  of 
Fishes,  Crustaceans,  etc.,  of  the  latter  that  took  place  during 
the  winter  of  1881-82  (A.  E.  Verrill). 

The  following  are  further  illustrations  of  the  work  of  life. 

3.  PEAT-FOKMATIONS. 

Peat  is  an  accumulation  of  half-decomposed  vegetable  mat- 
ter formed  in  wet  or  swampy  places.  In  temperate  climates 
it  is  due  mainly  to  the  growth  of  mosses  of  the  genus  Sphag- 
num. These  mosses  form  a  loose,  spongy  turf,  and,  as  they 
have  the  property  of  dying  at  the  extremities  of  the  roots 
while  increasing  above,  they  may  gradually  form  a  bed  of 
great  thickness.  The  roots  and  leaves  of  other  plants,  or 
their  branches  and  stumps,  and  any  other  vegetation  present, 
may  contribute  to  the  accumulating  bed.  The  small  Crusta- 
ceans, Worms,  and  various  other  kinds  of  species  living  in  the 
waters,  including  often  fresh-water  Sponges,  add  to  the  ma- 
terial ;  the  siliceous  spicules  of  the  sponges  may  generally  be 
found  in  the  ashes  of  the  peat.  The  carcasses  and  excrements 
of  large  animals  at  times  become  included.  Dust  may  also 
be  blown  over  the  marsh  by  the  winds. 

In  wet  parts  of  Alpine  regions  there  are  various  flowering 
plants  which  grow  in  the  form  of  a  close  turf,  and  give  rise 
to  beds  of  peat,  like  the  moss.  In  Fuecjia,  although  not  south 


76  DYNAMICAL  GEOLOGY. 

of  the  parallel  of  56°,  there  are  large  marshes  of  such  Alpine 
plants,  the  mean  temperature  being  about  40°  F. 

The  dead  and  wet  vegetable  mass  slowly  undergoes  a 
change,  becoming  an  imperfect  coal,  of  a  brownish-black 
color,  loose  in  texture,  and  often  friable,  although  commonly 
penetrated  with  rootlets.  In  the  change  the  woody  fibre  loses 
a  part  of  its  gases ;  but,  unlike  coal,  it  still  contains  usually 
25  to  33  per  cent  of  oxygen.  Occasionally  it  is  nearly  a  true 
coal. 

Peat-beds  cover  large  surfaces  of  some  countries,  and  occa- 
sionally have  a  thickness  of  forty  feet.  One  tenth  of  Ireland 
is  covered  by  them ;  and  one  of  the  "  mosses  "  of  the  Shannon 
is  stated  to  be  fifty  miles  long  and  two  or  three  broad.  A 
marsh  near  the  mouth  of  the  Loire  is  described  by  Blavier  as 
more  than  fifty  leagues  in  circumference.  Over  many  parts 
of  New  England  and  other  portions  of  North  America  there 
are  extensive  beds.  The  amount  in  Massachusetts  alone  has 
been  estimated  to  exceed- 120,000,000  of  cords.  Many  of  the 
marshes  were  originally  ponds  or  shallow  lakes,  and  gradually 
became  swamps  as  the  water,  from  some  cause,  diminished  in 
depth. 

Peat  is  often  underlaid  by  a  bed  of  whitish  shell  marl, 
consisting  of  fresh- water  shells  —  mostly  species  of  Limncea, 
Pliysa,  and  Planorbis  —  which  were  living  in  the  lake.  The 
beds  of  white  chalky  material  consisting  of  the  siliceous  shells 
of  Diatoms,  referred  to  on  page  67,  are  often  found  beneath 
peat. 

Peat  is  used  for  fuel,  and  also  as  a  fertilizer.  Mack  is 
another  name  of  peat,  and  is  used  especially  when  the  ma- 
terial is  employed  as  a  manure ;  but  it  includes  also  impure 
varieties  not  fit  for  burning,  being  applied  to  any  black  swamp- 
earth  consisting  largely  of  decomposed  vegetable  matter. 

Peat-beds  sometimes  contain  standing  trees  and  entire 
skeletons  of  animals  that  had  sunk  in  the  swamp.  The  peat- 
waters  have  often  an  antiseptic  power,  and  flesh  is  sometimes 
changed  by  the  burial  into  adipocere. 


CORAL-REEFS.  77 


4.  CORAL-REEFS. 

In  tropical  regions  corals  grow  in  vast  plantations  about 
most  oceanic  islands  and  along  the  shores  of  continents.  In 
the  shallow  waters  the  patches  or  groves  of  coral  are  usually 
distributed  among  larger  areas  of  coral  sand,  like  small  groves 
of  trees  or  shrubbery  in  some  sandy  plains. 

The  corals  have  much  resemblance  to  vegetation  in  their 
forms  and  their  modes  of  growth  ;  and  the  animals  are  so  like 
flowers  in  shape  and  bright  colors  that  they  are  often  called 
flower-animals  (page  184).  Along  with  the  corals  there  are 
also  great  numbers  of  Shells,  besides  Crabs,  Echini,  and  other 
kinds  of  marine  life. 

The  coral  plantations  are  swept  by  the  waves,  and  with 
great  force  when  the  seas  are  driven  by  storms.  The  corals 
are  thus  frequently  broken,  and  the  fragments  washed  about 
until  they  are  either  worn  to  sand  by  the  friction  of  piece 
upon  piece,  or  become  buried  in  the  holes  among  the  growing 
corals,  or  are  washed  up  on  the  beach.  Corals  are  not 
injured  by  mere  breaking,  any  more  than  is  vegetation  by  the 
clipping  of  a  branch ;  and  those  that  are  not  torn  up  from 
the  very  base  and  reduced  to  fragments  continue  to  grow. 

The  fragments  and  sand  made  by  the  waves,  and  by  the 
same  means  strewed  over  the  bottom,  along  with  the  shells 
also  of  mollusks,  commence  the  formation  of  a  bed  of  coral- 
rock,  —  literally  a  bed  of  limestone,  for  the  coral  and  shells 
have  the  composition  of  limestone,  —  and  consolidation  goes  on 
simultaneously.  As  the  corals  continue  growing  over  this 
bed,  fragments  and  sand  are  constantly  forming,  and  the  bed 
of  limestone  thus  increases  in  thickness.  In  this  manner  it 
goes  on  increasing  until  it  reaches  the  level  of  low  tide ;  be- 
yond this  it  rises  but  little,  because  corals  cannot  grow  where 
they  are  liable  to  be  left  for  a  day  wholly  out  of  water ;  and 
the  waves  have  too  great  force  at  this  level  to  allow  of  their 
holding  their  places,  if  they  were  able  to  stand  the  hot  and 
drying  sun.  A  bed  of  calcareous  rock  is  thus  produced  which 
is  a  coral  reef. 


78 


DYNAMICAL   GEOLOGY. 


Since  reef-corals  grow  to  a  depth  of  only  100  feet  (page 
74),  the  thickness  of  the  reef  cannot  much  exceed  100  feet 
if  the  sea-bottom  remains  at  a  constant  level,  except  where 
there  are  oceanic  currents  to  transport  to  greater  depths 
the  sand  that  is  made.  But  should  the  reef -region  be  slowly 
sinking,  at  a  rate  not  faster  than  the  corals  can  grow  and 
make  the  reef  rise,  then  almost  any  thickness  may  be  attained. 
From  observations  about  the  coral  regions  of  the  Pacific,  it  is 
supposed  that  some  of  the  reefs  have  acquired  a  thickness  of 
two  or  three  thousand  feet  or  more,  during  such  a  slow  sub- 
sidence. 

Fig.  89. 


View  of  a  high  island,  bordered  by  coral-reefs. 

The  coral  formations  of  the  Pacific  are  sometimes  broad 
reefs  around  hilly  or  mountainous  islands,  as  shown  in  the 
annexed  sketch.  To  the  left,  in  the  sketch,  there  is  an  inner 
reef  and  an  outer  reef,  separated  by  a  channel  of  water,  the 
inner  of  which  (/)  is  called  &  fringing  reef,  and  the  outer  (b) 

Fig.  90. 


Coral  island,  or  atoll. 

a  barrier  reef.  They  are  united  in  one  beneath  the  water. 
At  intervals  there  are  usually  openings  through  the  barrier 
reef,  as  at  h,  h,  which  are  entrances  to  harbors.  The  channels 
are  sometimes  deep  enough  for  ships  to  pass  from  harbor  to 
harbor. 


CORAL   ISLANDS.  79 

Many  coral-reefs  stand  alone  in  the  ocean,  far  from  any 
other  lands  (Fig.  90).  These  are  called  coral  islands  or  atolls. 

They  usually  consist  of  a  narrow  reef  encircling  a  salt- 
water lake.     The  lake  is  but  a  patch  of  ocean  enclosed  by  the 
reef   with   its   groves    of   palms   and   other 
tropical  plants.     When  there  are  deep  open- 
ings through  the  reef,  ships  may  enter  the 
lake,  or   lagoon  as  it  is  usually  called,  and    r'^ 
find  excellent  anchorage.     The  annexed  fig- 
ure (Fig.  91)  is  a  map  of  one  of  the  atolls 
of  the  Gilbert  (or  Kingsmill)  Islands  in  the 
Pacific.     The  reef  on  one  side  —  the  wind- 
ward— is  wooded  throughout;   but  on  the    Apia,  of  the  Gilbert 

group. 

other  it  has  only  a  few  wooded  islets,  the 

rest  being  bare  and  partly  washed  by  the  tides.     At  e  there 

is  an  opening  to  the  lagoon. 

The  Paumotu  Archipelago,  east-northeast  of  the  Society 
Islands,  contains  between  70  and  80  coral  islands ;  the  Caro- 
lines, with  the  Kadack,  Ralick,  and  Gilbert  groups  on  the 
east  and  southeast,  as  many  more ;  and  others  are  scattered 
over  the  intervening  ocean.  Most  of  the  high  islands  be- 
tween the  parallels  of  28°  north  and  south  of  the  equator 
(where  the  seas  are  sufficiently  warm,  page  74)  have  a  fringe 
of  coral-reefs. 

The  limestone  beds  made  from  corals  and  shells  are  not 
a  result  of  growth  alone,  as  in  the  case  of  the  deposits  formed 
from  microscopic  organisms,  but  of  growth  in  connection  with 
the  breaking  and  wearing  action  of  the  ocean's  waves  and  cur- 
rents. Corals  and  shells,  unaided,  could  make  only  an  open 
mass  full  of  large  holes,  and  not  a  solid  rock.  There  must 
be  sand  or  fine  fragments  at  hand,  such  as  the  waters  can  and 
do  constantly  make  in  such  regions,  in  order  to  fill  up  the 
spaces  or  interstices  between  the  corals  or  shells.  If  there  is 
clayey  or  ordinary  siliceous  sand  at  hand,  this  will  suffice, 
but  it  will  not  make  a  pure  limestone ;  in  order  to  have  the 
rock  a  true  limestone,  the  shells  and  corals  must  be  the 


80  DYNAMICAL   GEOLOGY. 

source  of  the  sand  or  fine  fragments,  for  these  alone  yield 
the  needed  calcareous  material  and  cement.  The  limestone 
made  in  this  way  by  the  help  of  the  waves  may  be,  and  often 
is,  as  fine-grained  as  a  piece  of  flint  or  any  ordinary  lime- 
stone, it  having  been  formed,  in  such  a  case,  of  the  finest 
coral  sand  or  mud.  In  other  cases,  it  contains  some  imbedded 
fragments  in  the  solid  bed ;  in  others,  it  is  a  coral  conglom- 
erate ;  and,  over  still  other  large  sheltered  areas,  it  is  a  mass 
of  standing  corals  with  the  interstices  filled  in  solid  with 
the  sand  and  fragments. 

Along  the  shores,  above  low  tide,  the  sands  are  aggluti- 
nated into  a  beach  sand-rock,  and  the  beds  have  the  slope 
of  the  beach,  or  5°  to  15°.  The  waters  contain  lime  (calcium 
bicarbonate)  in  solution  ;  and  as  the  sands,  wet  at  high  tide, 
dry  again  when  the  tide  is  out,  the  calcareous  cement  is 
deposited  between  the  grains,  and  so  consolidation  goes  for- 
ward. The  cement  coats  the  grains  with  carbonate  of  lime ; 
and  either  in  this  way,  or  by  its  own  concretionary  tenden- 
cies, the  rock  sometimes  becomes  an  oolyte  (page  37). 

The  process  of  limestone-making  now  going  on  through 
the  agency  of  coral  animals  illustrates  equally  the  method 
from  shells  and  crinoids.  The  extent  of  some  of  the  modern 
reefs  matches  nearly  that  of  the  largest  Paleozoic  reefs.  On 
the  north  of  the  Feejee  Islands  the  reef-grounds  are  5  to  15 
miles  in  width.  In  New  Caledonia  they  extend  150  miles 
north  of  the  island  and  50  miles  south,  making  a  total  length 
of  400  miles.  Along  Northeastern  Australia  they  stretch  on. 
although  with  many  interruptions,  for  1,000  miles. 


B.  Protective  and  Destructive  Effects. 

a.  Protective  Effects.  —  Slopes  are  protected  from  erosion 
through  a  covering  of  turf;  sand-hills,  from  the  winds, 
through  tufts  of  grass  and  other  vegetation ;  shores,  from  the 
surf  in  many  places,  by  a  growth  of  long  sea-weeds ;  and  the 


PROTECTIVE  AND  DESTRUCTIVE  EFFECTS.     81 

outer  margins  of  coral-reefs,  by  a  growth  over  the  exposed 
surface  of  calcareous  vegetation,  called  JSTullipores. 

Further,  forests  keep  a  vast  amount  of  moisture  in  the  wet 
ground  beneath  them,  which  is  gradually  supplied  to  the 
streams  as  from  a  reservoir,  making  them  serviceable  for 
mills  and  other  purposes  through  the  year ;  whereas,  if 
cut  away,  the  rains  fill  suddenly  the  river-channels,  pro- 
ducing disastrous  Hoods,  and  the  long  droughts  which  inter- 
vene are  seasons  of  dwindled  and  useless  waters.  And, 
besides,  the  floods  carry  away  the  soil  from  the  steep  hill- 
sides, and  may  reduce  a  productive  region  to  one  of  rocky 
ledges.  These  evils  are  already  a  reality  in  portions  of  North 
America,  and  are  on  the  increase. 

b.  Destructive  Effects.  —  Itocks,  where  jointed  or  fissured 
or  laminated,  are  torn  asunder  and  often  upturned  by  the 
growth  of  seed  in  a  crevice,  and  the  subsequent  enlarge- 
ment of  the  root  and  stem,  —  trunks  sometimes  growing  to  a 
diameter  of  several  feet  and  as  gradually  opening  the  crevice, 
and  thus  displacing  great  masses.  The  same  agency  opens 
crevices  to  moisture,  and  so  promotes  decomposition ;  and  it 
prepares  for  the  action  of  freezing  in  winter  (page  115). 

Boring  animals  cause  destruction  in  various  ways.  The 
mole,  mouse,  and  some  other  animals  tunnel  embankments, 
and  open  a  channel  for  the  exit  of  the  confined  waters,  which 
rapidly  enlarges ;  and  sometimes  a  vast  amount  of  erosion  is 
occasioned  by  the  waters  thus  discharged.  The  levees  of  the 
Mississippi  are  thus  tunnelled  by  crawfish,  occasioning  great 
floods  and  devastations.  Boring  shells,  as  the  Saxicavoc 
weaken  the  parts  of  rocks  exposed  to  the  surf. 

The  decay  of  vegetable  and  animal  matters  in  the  soil  pro- 
duces organic  acids  as  well  as  carbonic  acid,  which  erode 
rocks  and  promote  their  decomposition. 

The  preying  of  one  kind  of  life  on  another  has  had  great 
effect  toward  determining  the  prevalence,  or  the  dwindling 
and  destruction,  of  species,  besides  giving  occasion  for  adapta- 
tions to  new  conditions. 


82  DYNAMICAL  GEOLOGY. 


II.  CHEMICAL  ACTION  OF  THE  AIR  AND 
WATERS. 

Geological  work  of  a  destructive  kind  is  carried  forward  in 
a  quiet  way  through  the  chemical  action  of  the  constituents 
of  the  earth's  atmosphere  and  waters,  preparing  thus  for  the 
rougher  mechanical  work  of  these  agents ;  aud  the  same  pro- 
cesses have  their  formative  effects. 

1.  Oxygen  is  a  constituent  both  of  air  and  water,  it  being 
mixed  with  nitrogen  to  form  air,  and  combined  with  hydro- 
gen to  form  water  (H20);  and  many  substances  in  minerals 
or  rocks  have  an  intense  affinity  for  oxygen. 

a.  Iron  rusts  because  of  its  tendency  to  combine  with  oxy- 
gen ;  and  iron  in  the  protoxide  state  (FeO)  will  take  more 
oxygen,  and  so  pass  to  the  sesquioxide  state,  (Fe2Q3  —  FeC)*). 
Consequently,  a  mineral  containing  iron  in  the  former  state, 
like  pyroxene,  hornblende,  black  mica,   and  other  species, 
often  goes   to  destruction  through  this  affinity ;    and  hence 
rocks   containing  these   minerals  (like  trap)  usually  suffer 
easy  decomposition  ;    for  disturbing  one  constituent  is,  like 
taking  a  stone  from  an  arch,  destruction  to  the  whole.     The 
other  ingredients  of  the  iron-bearing  mineral  are  set  free  to 
make  earth,  and  commonly  the  associated  minerals  participate 
in  the  decay  and  add  to  the  earth.     The  iron  in  the  sesquiox- 
ide  state  makes  a  red  earth,  and  is  the  species  hematite.     But 
it  generally  combines  with  water,  and  becomes  a  brownish- 
yellow  earth  which   is   yellow  ochre,   or  the  mineral  called 
limonite ;  it  may  be  pure  limoriite,  but  it  is  usually  mixed 
with  the  other  materials  of  the  rock,  or  makes  ochreous  stains 
over  the  surfaces  of  fissures  or  joints. 

In  this  process  of  oxidation,  moisture  as  well  as  air  must 
be  present ;  the  oxygen  taken  up  is  usually  derived  from  the 
moisture. 

b.  Again,  iron  when  combined  with  sulphur,  constituting  a 
sulphide   of   iron,   like  pyrite    (FeS2),  or  pyrrhotite   (Fe»S8), 


CHEMICAL  CHANGES.  83 

oxidizes  readily  (unless  in  the  firmest  crystals),  and  passes  to 
the  same  state  of  yellow-ochre  or  limonite  (4FeS2  becoming 
2FeaOs+3H2O=2Fea3H,00).  The  sulphur  also  oxidizes  and 
becomes  sulphuric  acid,  which  is  a  destructive  agent,  owiner 

•*•  o  O 

to  its  tendency  to  take  into  combination  many  of  the  ingre- 
dients of  minerals,  as  lime,  magnesia,  soda,  potash,  alumina, 
and  also  iron  ;  and  it  hence  aids  much  in  the  work  of  destruc- 
tion. This  acid  may  combine  with  the  iron,  and  so  make 
green  vitriol ;  but  as  its  affinity  for  the  substances  above  enu- 
merated is  stronger  than  for  iron,  the  iron  is  usually  left  in 
the  ochreous  state. 

Now  sulphide  of  iron,  in  the  form  of  pyrite  or  pyrrhotite, 
is  disseminated  more  or  less  abundantly  through  nearly  all 
the  rocks  of  the  globe,  occurring  in  most  granite,  syenyte, 
gneiss,  mica  and  other  schists,  and  slates,  sandstones,  shales, 
much  trap,  and  many  limestones  ;  and  hence,  rocks  in  all 
lands  are  undergoing  destruction  through  this  agency.  Many 
a  fair-looking  building-stone  is  rendered  worthless  by  it.  It 
is  the  mostjmiversal  of  rock-destroyers.  When  the  minute 
grains  of  pyrite  in  a  granite  or  sandstone  oxidize,  the  other 
mineral  particles  of  the  rock  are  set  loose  and  become  discol- 
ored with  the  ochre  that  is  made ;  and  the  sulphuric  acid,  at 
the  same  time  formed,  eats  into  some  of  those  grains  to  cause 
their  decomposition.  Thus  the  granite  either  (a)  disintegrates 
into  a  loose  granitic  sand,  or  (b)  it  becomes  decomposed  to 
earth  or  clay.  Blocks  of  trap  have  a  thin  decomposed  crust 
which  is  incessantly  receiving  additions  inside  while  losing 
outside. 

The  decomposition  of  sulphide  of  iron  in  shales  or  clays 
often  forms  alum,  and  makes  alum-clays,  because  of  the  com- 
bination of  the  sulphuric  acid  with  the  alumina  of  the  rock, 
and  usually  with  some  other  base  in  the  protoxide  state,  as 
potash,  soda,  magnesia  etc. 

2.  Carbonic  Acid  (C02)  is  present  in  the  atmosphere,  about 
3  parts  in  10,000  by  volume  consisting  of  this  gas.  It  is 
present  in  all  rain-water,  the  rain-water  deriving  it  from  the 


84  DYNAMICAL  GEOLOGY. 

atmosphere.  It  is  present  in  the  soil,  being  produced  where 
the  material  of  plants  and  animals  is  undergoing  slow  decom- 
position; and  thence  it  is  given  to  the  waters  percolating 
through  soils.  By  all  the  methods  mentioned,  and  also 
through  animal  respiration,  the  sea  derives  carbonic  acid. 
Moreover,  in  the  earlier  ages  of  the  globe,  the  amount  of 
carbonic  acid  in  the  atmosphere  and  waters  far  exceeded  the 
present. 

Carbonic  acid  tends  strongly  to  form  combinations  with 
magnesia,  lime,  potash,  soda,  and  with  iron  in  the  protoxide, 
state.  Hence  a  feldspar,  since  it  yields  potash,  soda,  or  lime, 
is  liable  to  have  its  alkali  carried  off  by  percolating  waters  ; 
and  with  such  a  loss,  the  mineral  changes  to  a  hydrous  clayey 
mineral  called  kaolin,  —  the  material  used  in  making  porce- 
lain. Common  feldspar  yields  on  analysis  17  per  cent  of 
potash,  18.5  of  alumina,  and  645  of  silica;  and  kaolin,  no 
potash,  14  of  water,  40  of  alumina,  and  46  of  silica.  Granite 
and  other  rocks  are  often  eaten  into  by  this  process,  so  as  to 
be  fragile  to  the  depth  of  a  foot  or  more,  and  sometimes  to  a 
depth  of  50  or  100  feet. 

Fig.  92.  Fig.  93. 


The  depth  of  decomposition,  by  either  method,  is  measured 
by  the  depth  to  which  moisture  is  absorbed;  so  that  the 
architectural  value  of  a  stone  is  inversely  as  its  absorbent 
quality.  All  cracks  or  joints  by  which  water  enters  may 
have  a  discolored  border  of  like  depth  (Fig.  92);  and  the 
process  goes  on  by  this  means,  in  some  granite,  trap,  and  other 
rocks,  until  the  mass  becomes  reduced  to  what  looks  like  a 
pile  of  large  spheroidal  concretions  (Fig.  93);  and  ends  finally 
in  making  earth,  or  loose  sand,  of  the  whole. 


CHEMICAL    CHANGES.  85 

When  the  iron-carbonate  (called  siderite)  is  left  exposed  to 
the  air  and  moisture,  the  iron  oxidizes,  and  changes  to  limon- 
ite.  So  any  limestone  that  contains  iron,  replacing  part  of 
the  calcium  or  magnesium,  will  readily  become  brown  and 
crumble. 

The  decomposition  of  iron-bearing  minerals  is  promoted  by 
the  action  of  carbonic  acid,  or  of  an  organic  acid  derived  from 
the  soil  waters.  These  acids  extract  the  iron  protoxide  and 
make  with  it  a  soluble  salt  of  iron,  and  thus,  by  the  aid  of 
streamlets,  may  carry  the  iron  away.  In  order  that  carbonic 
acid  should  thus  take  up  iron,  and  make  the  soluble  bicarbon- 
ate, it  must  be  under  pressure,  and  the  carriers  now  are  the 
organic  acids  ;  but  in  ancient  time,  when  the  atmosphere 
was  much  denser  than  at  present,  carbonic  acid  may  have 
done  this  work.  The  salt  of  iron  becomes  oxidized  in  the 
low  places  or  marshes  to  which  it  may  be  carried,  because 
the  waters  thus  get  more  of  the  salt  that  they  can  dissolve, 
and  forms  there  a  yellow  or  brown  or  brownish-black  deposit 
of  limonite  or  a  related  ore. 

The  organic  material  of  the  soils,  owing  to  its  using  oxygen 
when  decomposing,  will  take  it  from  any  Fe.203  present,  and 
may  thus  change  it  to  Fe  0,  and  this  Fe  O  then  combine 
with  the  organic  acid-  or  carbonic  acid  at  hand.  Many  red 
beds  of  rocks  have  lost  the  red  color  in  spots  or  seams  or 
along  cracks,  by  this  method  of  deoxidation. 

Waters  containing  carbonic  acid  readily  erode  limestone. 
The  limestone  is  taken  up  and  a  calcium  bicarbonate  is  formed, 
which  is  soluble.  On  evaporation,  the  bicarbonate  loses  its 
excess  of  carbonic  acid,  and  the  limestone  taken  up  is  again  de- 
posited. Thus  limestone  strata  are  eroded,  and  caverns  made  ; 
and  through  the  depositions,  the  caverns  are  hung  with  stalac- 
tites and  floored  with  stalagmite.  (See  pages  102,  104). 

Deposits  formed;  Rocks  consolidated.  —  (1)  By  the  processes 
above-mentioned,  from  iron-bearing  limestone  or  iron  carbon- 
ate, great  beds  of  limonite,  of  the  purest  quality,  have  been 
made  (some,  over  100  feet  deep) ;  and  they  often  lie  in  place, 


86  DYNAMICAL  GEOLOGY. 

that  is.  occupy  the  depressions  produced  by  the  decomposi- 
tion. Those  of  Richmond  and  West  Stockbridge  in  Massa- 
chusetts, of  Salisbury  in  Connecticut,  of  Millerton  and  other 
places  in  eastern  New  York,  and  of  many  localities  south  of 
New  York  in  Pennsylvania  and  Virginia,  are  of  this  kind. 
Again,  the  iron-salts  carried  to  marshes  —  the  pockets  of  a 
region  —  have  often  made  large  beds  of  the  related  bog 
ore ;  but  such  ore  is  likely  to  contain  sulphur  (from  decom- 
posed pyrite)  and  phosphorus  (from  the  decomposing  organic 
material  present)  and  hence  the  iron  afforded  is  of  inferior 
quality. 

(2)  From  the  feldspar  decompositions  have  come  large  beds 
of  kaolin ;  and  some  of  the  best  and  largest  have  been  made 
from  quartzytes  containing  disseminated  feldspar,  as  in  the 
southern  margin  of  New  Marlborough,  Mass. 

(3)  Carbonated  waters,  besides   forming   stalactites,  have 
made  large  beds  of  limestone,  like  the  travertine  of  JTivoli, 
near  Rome,  and  the  so-called  alabaster  of  Mexico. 

Carbonated  waters,  besides  serving  in  the  consolidation  of 
limestones  (page  80),  often  also  consolidate  sand-beds,  gravel- 
beds,  and  clay-beds,  when  grains  of  limestone  are  even  sparingly 
present;  and  very  commonly  the  solidification  takes  place 
around  centres  (some  grain,  or  it  may  be  fossil,  serving  as 
the  nucleus)  and  so  makes  concretions  (page  47)  in  the  bed, 
complete  consolidation  often,  following  later.  Again,  consoli- 
dation takes  place  to  some  extent  through  depositions  of 
limonite  in  pebble-beds  and  sand-beds.  But  the  more  com- 
mon method  of  solidifying  such  fragmental  deposits  is  through 
siliceous  waters  (page  147). 

III.  THE  ATMOSPHERE. 

The  following  are  some  of  the  mechanical  effects  connected 
with  the  movements  of  the  atmosphere. 

1.  Transportation  of  sand,  dust,  etc.  —  The  streets  of  most 
cities,  as  well  as  the  roads  of  the  country,  in  a  dry  summer 


WORK   OF  THE  WINDS.  87 

day,  afford  examples  of  the  drift  of  dust  by  the  winds.  The 
dust  is  borne  most  abundantly  in  the  direction  of  the  preva- 
lent winds,  and  may  in  the  course  of  time  make  deep  beds. 
The  dust  that  finds  its  way  through  the  windows  into  a  neg- 
lected room  indicates  what  may  be  done  in  the  progress  of 
centuries  where  circumstances  are  more  favorable. 

The  moving  sands  of  a  desert  or  sea-coast  afford  the  more 
important  examples  of  this  kind  of  action. 

On  sea-shores,  where  there  is  a  sea-beach,  the  loose  sands 
composing  it  are  driven  inland  by  the  winds  into  parallel 
ridges  higher  than  the  beach,  forming  drift-sand  hills.  They 
are  grouped  somewhat  irregularly,  owing  to  the  course  of  the 
wind  among  them,  and  also  to  little  inequalities  of  compact- 
ness, or  to  protection  from  vegetation.  They  form  especially 
(1)  where  the  sand  is  almost  purely  siliceous,  and  therefore 
not  at  all  adhesive  even  when  wet,  and  not  good  for  giving 
root  to  grasses ;  and  (2)  on  windward  coasts.  They  are  com- 
mon on  the  windward  side,  and  especially  the  projecting 
points,  even  those  of  a  coral  island,  but  never  occur  on  the 
leeward  side,  unless  this  side  is  the  windward  during  some 
portion  of  the  year.  The  stratification  in  such  drift-hills  is 
of  the  kind  represented  in  Fig.  22  /,  page  45,  and  shows  that 
the  growing  hill  was  often  cut  partly  down  or  through  by 
storms,  and  was  again  and  again  completed  after  such  dis- 
asters. On  the  southern  shore  of  Long  Island  series  of  such 
sand-hills,  10  to  30  feet  high,  extend  along  for  100  miles. 
They  are  partially  anchored  by  straggling  tufts  of  grass.  The 
coast  of  New  Jersey  down  to  the  Chesapeake  is  similarly 
fronted  by  sand-hills.  They  occur  also  on  the  east  coast  of 
Lake  Michigan.  In  Norfolk,  England,  between  Hunstanton 
and  Weybourne,  the  sand-hills  are  50  to  60  feet  high. 

Dust  is  carried  by  storm  winds,  sometimes  hundreds  of 
miles.  A  shower  covered  the  Cape  Verdes  with  dust  from 
Africa,  nearly  1,000  miles  distant,  and  was  1,600  miles  broad 
(Darwin).  Volcanic  dust  was  carried,  in  1835,  from  Guate- 
mala to  Jamaica,  800  miles.  Birds  and  insects  are  thus  car 


88  DYNAMICAL  GEOLOGY. 

ried  to  sea.  In  one  dust-shower,  about  Lyons  in  France, 
720,000  pounds  of  dust  fell,  and,  of  this,  90,000  consisted  of 
Diatoms  and  other  organic  relics  (Ehrenberg). 

2.  Additions  to  land  by  means  of  drift-sands.  —  The  drift- 
sand  hills  are  a  means  of  recovering  lands  from  the  sea.     The 
appearance  of  a  bank  at  the  water's  surface  off  an  estuary  at 
the  mouth  of  a  stream  is  followed  by  the  formation  of  a  beach, 
and  then  the  raising  of  hills  of  sand  by  the  winds,  which 
enlarge  till  they  sometimes  close  up  the  estuary,  exclude  the 
tides,  and  thus  aid  in  the  recovery  of  the  land  by  the  deposi- 
tions of  river-detritus.      Lyell  observes  that  at  Yarmouth, 
England,  thousands  of   acres  of  cultivated  land  have  thus 
been  gained  from  a  former  estuary.     In  all  such  results  the 
action  of  the  waves  in  first  forming  the  beach  is  a  very  impor- 
tant part  of  the  whole. 

3.  Destructive  effects  of  drift-sands.  —  Dunes.  —  Dunes    are 
regions  of  loose  drift-sand.     In  Norfolk,   England,  between 
Hunstanton  and  Weybourne,  the  drift-sands  have  travelled 
inland   with   great   destructive   effects,   burying    farms   and 
houses.      They  reach,  however,  but  a  few  miles  from  the 
coast-line,  and  were  it  not  that  the  sea-shore  itself  is  being 
undermined  by  the  waves,  and  is  thus  moving  landward,  the 
effects  would  soon  reach  their  limit.     East  of  Lake  Michigan 
the  sand-hills  have  a  height  of  100  to  200  feet;  and  even 
215  feet  at  Grand  Haven,  where,  according  to  A.  Winchell, 
the  forest  has  been  buried  so  as  to  leave  only  the  "  withered 
tree-tops  projecting  a  few  feet  above  the  waste  of   sands." 
In  the  desert  latitudes,  drift-sands  are  more  extended  in  their 
effects. 

4.  Abrasion ;    Sand-scratches.  —  The   sands   carried   by   the 
winds,  when  passing  over  rocks,  sometimes  wear  them  smooth, 
or  cover  the  surface  with  scratches  and  furrows,  as  observed 
by  W.  P.  Blake  on  granite  rocks  at  the  Pass  of  San  Bernar- 
dino  in  California.      Ledges  and   bluffs   have   been  deeply 
eroded  and  shaped  or  worn  away  by  this  agency.     Similar 
effects  have  been  observed  by  Winchell  in  the  Grand  Traverse 


WORK  OF   THE  WINDS.  89 

region,  Michigan.  Glass  in  the  windows  of  houses  on  Cape 
Cod  sometimes  has  holes  worn  through  it  by  the  same  means. 
The  hint  from  nature  has  led  to  the  use  of  sand,  driven  by 
a  blast  with  or  without  steam,  for  cutting  and  engraving 
glass,  and  even  for  cutting  and  carving  granite  and  other 
hard  rocks. 

5.  Winds  as  transporters  of  Moisture. — The  atmosphere  takes 
moisture  from  the  ocean  and  land,  proportionally  to  its  tem- 
perature, and  transports  it.  If  the  air  increases  in  tem- 
perature as  it  passes  over  a  continent,  it  keeps  taking  up 
moisture,  and  so  dries  up  the  land ;  if,  on  the  contrary,  it 
loses  in  temperature,  its  capacity  for  moisture  is  lessened, 
and  it  drops  it,  making  rain  and  mists  over  the  land.  If  the 
warm  wind  strikes  the  cold  side  or  summit  of  a  mountain, 
the  moisture  is  largely  dropped,  so  that  little  remains  for  the 
region  on  the  opposite  side  of  the  mountain,  which  therefore 
experiences  drought. 

The  trade  winds  are  movements  of  the  air  within  the 
tropics  westward,  against  the  east  side  of  the  continents; 
they  are  warm  winds,  well  charged  with  moisture.  Near 
and  over  the  continents  they  bend  away  from  the  equator 
and  thus  pass  to  colder  regions ;  hence  they  are  moist  winds, 
giving  abundant  rains.  Consequently  the  eastern  portions  of 
continents  are  regions  of  much  rain ;  and  the  farther  back 
from  the  east  coast  the  higher  mountains  are  set  the  larger 
the  surface  benefited  by  the  rains.  The  great  Gulf  of  Mexico 
is  of  immense  service  to  North  America  as  a  source  of  water- 
supply  to  the  winds ;  and  so  also  is  the  position  of  the  high 
Rocky  Mountains,  so  far  away  from  the  eastern  coast. 

The  winds  over  the  ocean,  north  of  the  parallel  of  30°  to 
60°,  are  movements  of  air  eastward,  and  therefore  against  the 
west  side  of  the  continents ;  they  are  not  warm  winds,  and 
not  abundant  in  moisture.  Near  and  over  the  continents 
they  bend  equator-ward  and  pass  generally  over  warmer 
regions ;  hence  they  are  drying  winds ;  and  consequently  the 
western  portions  of  continents  are  regions  of  less  rain  than 


90  DYNAMICAL    GEOLOGY. 

the  eastern ;  and  on  the  western  portions,  between  latitudes 
25°  and  35°  exist  the  chief  desert  regions  of  the  continental 
borders. 

Thus  the  winds  are  largely  the  distributers  of  fertility,  the 
locators  of  great  forest  regions  and  deserts,  and  the  limiters  of 
distribution  for  the  living  species  of  the  land ;  and  they  have 
done  their  work  in  the  same  way  essentially  through  all  past 
time,  and  in  general  with  like  geographical  effects  over  the 
same  regions  from  one  age  to  another.  America  has  always 
been,  as  Guyot  has  styled  it,  the  forest  continent. 

IV.  — WATER. 

The  following  subdivisions  are  here  adopted :  — 

1.  FRESH  WATERS  ;  or  those  of  Eivers  and  Lakes. 

2.  The  OCEAN  ;  and,  with  it,  the  larger  Lakes. 

3.  FROZEN  WATERS,  or  Glaciers  and  Icebergs. 

1.  Fresh  Waters. 

A.   Superficial  Waters,  or  Rivers. 

The  working  force  or  energy  of  moving  waters  depends  on 
gravity,  and  is  determined,  in  any  case,  by  (1)  the  volume  of 
water  and  (2)  the  amount  of  its  fall.  This  energy  may  be 
used  up  (1)  in  overcoming  the  friction  due  directly  to  the 
motion,  —  in  which  erosion  of  the  bed  may  be  produced; 
(2)  in  transporting  earth  or  stones,  —  the  source  of  most  frag- 
mental  deposits;  and  (3)  in  overcoming  the  friction  arising 
from  the  abrasion  of  the  particles  of  the  transported  material 
against  the  bed  and  among  themselves,  —  another  source  of 
erosion. 

I.  Erosion. 

1.  Sources  of  streams;  Drainage-areas.  —  The  waters  of  riv- 
ers descend  in  the  form  of  rain  and  snow  from  the  clouds, 
and  are  derived  by  evaporation_both  from  the  surface  of  the 


RIVERS.  91 

land,  with  its  lakes,  rivers,  and  foliage,  and  from  the  ocean, 
but  mostly  from  the  latter.  The  waters  rise  into  the  upper 
regions  of  the  atmosphere,  and,  becoming  condensed  into 
drops  or  snow-Hakes,  fall  over  the  hills  and  plains.  They 
gather  first  into  rills ;  these,  as  they  descend,  unite  into 
rivulets ;  these,  again,  if  the  region  is  elevated  or  mountain- 
ous, into  torrents ;  torrents,  flowing  down  the  different  moun- 
tain valleys,  combine  with  other  torrents  to  form  rivers ;  and 
rivers  from  one  mountain-chain  sometimes  join  the  rivers 
from  another  and  make  a  common  stream  of  great  magnitude, 
and  great  drainage-area,  like  the  Mississippi  or  the  Amazon. 

The  Mississippi  has  its  tributaries  among  all  the  eastern 
heights  of  the  great  Kocky  Mountain  chain,  throughout  a 
distance  of  1,000  miles,  or  between  the  parallels  of  35°  N. 
and  50°  N. ;  and  still  another  set  of  tributaries  gather  waters 
from  the  Appalachian  chain,  between  Western  New  York  and 
Alabama,  Kills,  rivulets,  torrents,  and  rivers  combine  over 
an  area  of  millions  of  square  miles  to  make  the  great  central 
trunk  of  the  North  American  continent. 

The  amount  of  water  poured  each  year  into  the  ocean  by 
the  Mississippi  averages  19J  trillions  (19,500,000,000,000) 
of  cubic  feet,  varying  from  11  trillions  in  dry  years  to  27  tril- 
lions in  wet  years.  This  amount  is  about  25  per  cent  of  that 
furnished  by  the  rains,  the  rest  being  lost  mostly  by  direct 
evaporation,  but  also  in  part  by  absorption  into  the  soil  and 
strata  and  by  contributing  to  the  growth  of  vegetation. 

Snowy  mountains  deal  out  water  gradually  under  the 
control  of  the  sun  and  winds,  day  and  night  and  summer  and 
winter  making  alternations  in  the  supply  to  the  streams. 
Forest  regions  also  are  like  reservoirs  in  holding  on  long,  and 
supplying  gradually,  the  waters  beneath  them. 

2.  Erosion.  Valley-making.  —  Erosion  or  wear  (termed  also 
denudation)  and  transportation  are  consequences  of  motion. 
The  rain-drop  makes  an  impression  where  it  falls  (Fig.  27, 
page  47) ;  the  rill  and  rivulet  carry  off  light  sand  and  deepen 
their  beds,  as  may  be  seen  on  any  sand-bank  or  by  many  a 


92  DYNAMICAL  GEOLOGY. 

roadside ;  torrents  work  with  greater  power,  tearing  up  rocks 
and  trees  as  they  plunge  along,  and,  in  the  course  of  time, 
make  deep  gorges  or  valleys  in  the  mountain-slopes ;  and 
rivers,  especially  in  periods  of  flood,  hurry  on  with  vast 
power,  making  wider  valleys  over  the  breadth  of  a  continent. 
The  slopes  of  a  lofty  mountain,  exposed  through  ages  to  the 
action  described,  finally  become  reduced  to  a  series  of  valleys 
and  ridges,  and  the  summit  often  to  towering  peaks  and 
crested  heights,  —  all  these  effects  originating  in  the  fall  of 
rain-drops  or  snow-flakes. 

Flood-time  is  the  period  of  active  work.  Before,  streams  are 
often  almost  still  from  (1)  want  of  slope,  or  (2)  the  friction  be- 
tween the  large  bed  and  the  little  water ;  but  at  flood-height 
the  waters  at  their  high  level  have  (1)  augmented  slope,  and, 
(2)  relatively  to  the  amount  of  water,  largely  diminished 
friction  ;  and  hence  comes  the  greater  velocity.  The  Connect- 
icut, to  Hartford,  36  miles  (in  an  air  line),  is  a  tidal  stream, 
zero  in  working  force  at  low  water  and  tide ;  but  in  its 
highest  flood  (30  feet  at  Hartford)  it  has  a  mean  pitch  to  the 
Sound  of  10  inches  a  mile,  and  flows  off  with  great  rapidity. 
On  mountain  streams  the  transition  is  often  from  almost  or 
quite  zero  to  a  succession  of  cataracts  of  vast  working  force. 

Nearly  all  the  deep  valleys  of  the  world  owe  their  excava- 
tion to  running  water.  Their  positions  have  sometimes  been 
determined  by  fissures  in  the  earth's  strata,  or  by  the  courses 
of  the  lowlands  left  between  mountain  chains ;  but,  generally, 
rivers  have  worked  out  their  own  channels  from  their  begin- 
nings onward  to  their  present  depth  and  extent. 

With  steep  slope,  as  in  many  mountain  regions,  the  stream 
excavates  rapidly,  and  carries  off  what  it  gathers  instead  of 
depositing  it,  the  powers  of  erosion  and  transportation  being 
great ;  consequently  the  valley  it  makes  is  more  or  less 
V-shaped.  But,  where  the  slope  is  gentle  and  the  velocity 
small,  the  erosion  at  bottom  becomes  feeble  or  null ;  in  times 
of  flood  the  waters  spread  over  the  banks  and  tend  to  widen 
the  valley  as  they  rush  along  by  its  sides;  at  the  same 


EROSION   BY  RIVERS.  93 

time,  with  declining  floods  and  slackening  velocity,  deposi- 
tions take  place  of  the  transported  material,  owing  to  fric- 
tion, making  an  alluvial  flat,  or  flood-plain,  where  the 
retardation  is  greatest  on  one  or  both  sides,  and  so  the 
valley  becomes  U-shaped.  Eivers,  hence,  have  ordinarily  a 
narrow  channel  for  the  dry  season,  and  a  wide  flood-plain 
which  is  its  bottom  in  time  of  flood. 

3.  Methods  of  Erosion.  —  Erosion  is  carried  forward  mainly 
by  the  following  methods  :  — 

a.  By  the  friction  or  strokes  of  the  flowing  waters.  —  In  a 
rapid  stream,  especially  when  increased  in  depth  and  speed  by 
floods,  the  waters  often  throw  themselves  in  large  volumes  into 
cavities  or  recesses  among  the  rocks,  and  thus  tear  away  ob- 
stacles, overcome  cohesion  in  the  softer  deposits  within  reach, 
wrench  out  masses  of  rock  where  the  beds  are  laminated  or 
jointed  (and  nearly  all  rocks  are  jointed),  and  by  this  means, 
and  by  undermining,  make  rapid  destruction  of  exposed  ledges 
and  piles  of  strata,  and  so  carry  on  the  excavation  of  tlis 
channel.     Where  the  pitch  is  large,  the  waters  accumulate 
working-force  by  the  descent,  augmenting  the  effects.     Over 
smoothly  rounded  or  even  surfaces,  the  effect  is  very  feeble. 

b.  Bi/  the  abrading  action  of  transported  earth  and  stones.  — 
The  earth  and  stones  carried  along  by  a  stream  abrade  the 
bottom  and  sides  of  the  channel,  and  so  carry  forward   the 
work  of  excavation.     There  is  mutual  abrasion  of  the  earth 
and  stones,  resulting  in  increasing  their  fineness  and  their 
transportability.     A  stream  seldom  does  so  much  transport- 
ing work  as  to  lose  all  abrading  power,  and  never  when  a 
large  and  rapid  torrent. 

c.  Aid  from  decomposition  and  solution. — The  decompos- 
ing and  dissolving  action  of  the  water  takes  an  important  part 
in  the  work  of  denudation.      Decomposition  and  disintegra- 
tion (pp.  82-35)  are  going  on  over  almost  all  exposed  surfaces 
of  rocks,  thus  making  softened  material  for  the  abrading  and 
transporting  rills  and  rivers.      Solution  also  has  large  effects, 
especially  in  limestone  regions  ;  it  helps  greatly  in  the  exca- 


94  DYNAMICAL   GEOLOGY. 

vation  of  valleys,  and  finds  in  the  joints  of  the  rocks  a  chance 
to  begin  the  work  (page  84). 

The  rounded  stones,  gravel,  and  earth  of  fields,  and  also  the 
material  of  most  geological  formations,  has  been  made  out  of 
pre-existing  solid  rocks,  to  a  large  degree  by  the  wearing  action 
of  waters,  —  either  those  of  streams  over  the  land,  or  those  of 
the  ocean.  But  this  action  is,  and  ever  has  been,  greatly  aided 
by  the  processes  of  decomposition  or  disaggregation  due  to 
the  elements.  This  last-mentioned  cause  is  sufficient  alone  to 
turn  angular  blocks  of  most  rocks  into  rounded  masses. 

The  finer  transported  material  is  called  detritus  (from 
the  Latin  for  worn  out}  and  also  silt.  The  larger  rounded 
stones  are  termed  bowlders. 

4.  Cascades,  —  A  cascade  usually  occurs  on  a  rapid  stream, 
where  in  the  course  of  it  there  is  a  hard  bed  of  rock  over- 
lying  a  soft  one.     The  hard  bed  resists  wear,  while  the  soft 
one  below  yields  easily :    thus  a  plunge  begins,  which  in- 
creases in  force  as  it  increases  in  extent.     At  Niagara  Falls, 
80  feet  of  shale  under-lie  80  feet  of  hard  limestone  (Fig.  14, 
p.  40).     Kills  and  rivulets  made  by  a  shower  of  rain  along 
road -sides  or  sand-banks  often  illustrate  also  this  feature  of 
great  mountain-streams. 

5.  Features    produced  where    Strata  are    nearly    Horizontal. 
Mountains  of  Circumdenudation. — When  the  rocks  underlying 
a  region  are  nearly  horizontal,  the  valleys  cut  by  the  rivers 
have  usually  bold  rocky  sides.     In  many  parts  of  the  Eocky 
Mountains  the  streams  have  worked  their  way  down  through 
the  rocks  for  hundreds,  and  in  some  places  even  thousands,  of 
feet.     Such  a  place  is  often  called  a  canon. 

These  canons  are  of  wonderful  depth  and  magnitude  on  the 
Colorado  Eiver,  over  the  west  slope  of  the  Eocky  Mountains, 
between  longitude  111°  W.  and  115°  W.  For  300  miles  there 
is  a  nearly  continuous  canon,  3,500  to  6,000  feet  deep.  The 
following  sketch,  from  one  of  the  excellent  photographs  of  the 
region  by  the  artist  of  Powell's  Expedition,  represents  a  por- 
tion of  it,  called  the  Marble  Canon.  The  rocks  stand  in 


CANONS;   MOUNTAIN-SCULPTURE.  95 

nearly  vertical  precipices  either  side  of  the  stream,  and  the 
height  above  the  water  to  the  top  of  the  bluff'  seen  in  the 
distance  is  5,000  feet.  The  deep  gorge  is  the  result  of  erosion 
by  the  stream,  which  is  still  continuing  its  wearing  action. 

Fig.  94. 


Cailon  of  the  Colorado. 

In  large  parts  of  the  canon  are  crowds  of  peaks  and 
temple-shaped  summits,  some  of  them  5,000  feet  high,  all  of 
which  are  the  work  of  the  waters  since  the  era  of  the  early 
Tertiary.  Moreover,  above  the  walls  of  the  canon,  over  the 
country  to  the  northward,  rise  plateaus  and  mountains,  in 
which  the  strata  are  piled  up  to  an  additional  altitude  of 
5,000  to  7,000  feet,  which  are  portions  of  great  formations 
that  once  spread  over  the  whole  region.  The  mountain  ridges 
and  peaks  of  Colorado,  Uta.h,  and  the  adjoining  territories,, 


96  DYNAMICAL  GEOLOGY. 

12,000  to  14,000  feet  in.  height,  are  other  fragments  of  the 
same  strata,  and  often  show  nearly  horizontal  beds  to  their 
tops. 

When  mountain  forms  have  thus  been  made  they  are  some- 
times called  'mountains  of  circumdenudation.  Given  a  great 
elevated  plateau  in  a  region  of  rains,  and  mountain-sculpturing 
will  go  on  about  it,  and  may  continue  until  all  is  ridge  and 
valley,  not  a  square  mile  of  the  original  plateau  retaining  its 
flat  surface  ;  and  the  resulting  crested  ridges  may  rise  thou- 
sands of  feet  above  the  bottoms  of  the  valleys,  if  the  plateau 
is  one  of  sufficient  height.  The  Catskill  Mountains,  New 
York,  are  an  example  of  a  mountain  of  circumdenudation ; 
and  most  of  the  mountains  of  Utah  and  Colorado  are  other 
examples.  The  wear  is  much  the  most  rapid  when  there  is 
little  vegetation  over  the  surface. 

The  following  figures,  by  Lesley,  illustrate  some  of  the 
results  of  the  sculpturing  by  water,  in  both  horizontal  and 
upturned  or  flexed  strata.  In  the  production  of  such  eleva- 
tions, the  ocean  has  sometimes  taken  part  during  the  sub- 
mergence of  a  continent ;  but  the  final  results  are,  in  almost 
all  cases,  due  to  the  chisellings  of  fresh  waters.  The  figures 
here  given  are  small,  but  the  elevations  they  represent,  as 
illustrated  in  the  Appalachians,  Juras,  and  many  other  moun- 
tain regions,  are  often  thousands  of  feet  in  height. 

When  the  beds  are  horizontal,  or  nearly  so,  but  of  unequal 
hardness,  the  softer  strata  are  easily  worn  away,  and  by  this 
means  the  harder  strata  become  undermined.  Table-lands 

Fig.  95.  Fig.  96. 


are  often  thus  formed,  having  a  top  of  the  harder  rock,  and 
the  declivities  usually  banded  with  projecting  shelves  and 
intervening  slopes.  Figs.  95,  96  represent  the  common 
character  of  such  hills.  Such  flat-topped  elevations  in  the 


or  THE  X 
V;4»V£KG{TY  } 
k  WATER. 


97 


Colorado  region  have  been  called  mesas,  from  the  Spanish 
for  table. 

When  the  beds  are  inclined  between  5°  and  30°,  and  are 
alike  in  hardness,  there  is  a  tendency  to  make  hills  with  a 
long  back  slope  and  bold  front ;  but  with  a  much  larger  dip, 
the  rocks,  if  hard,  often  outcrop  in  naked  ledges. 

When  the  dipping  strata  are  of  unequal  hardness,  and  lie 
in  folds,  there  is  a  wide  diversity  in  the  results  on  the  fea- 
tures of  the  landscape. 

Figs.  97,  98  represent  the  effects  from  the  erosion  of  a 
synclinal  region  consisting  of  alternations  of  hard  and  soft 

Figs.  97-102. 


strata.     The  protection  of  the  softer  beds  by  the  harder  is 
well  shown.     This  is  still  further  exhibited  in  Figs.  99-102. 

Anticlinal  strata  give  rise  to  another  series  of  forms,  in 
part  the  reverse  of  the  preceding,  and  equally  varied.  Figs. 
103-106  represent  some  of  the  simpler  cases.  When  the 
back  of  an  anticlinal  mountain  is  divided  (as  in  Figs.  103— 
105),  the  mountain  loses  the  anticlinal  feature,  and  the 


Figs.  103-106. 


parts  are  simply  monoclinal  ridges.  Tn  Fig.  106  the  anti- 
clinal character  is  distinct  in  the  central  portion,  while  lost  in 
the  parts  on  either  side.  In  Fig.  106,  to  the  right,  a  common 
effect  is  shown  of  the  protection  afforded  to  softer  layers  by 

7  . 


98  DYNAMICAL   GEOLOGY. 

even  a  vertical  layer  of  hard  rock:  the  vertical  layer  forms 
the  axis  of  a  low  ridge. 


2.  Transportation    by  Rivers,  and  distribution  of  trans- 
ported Material. 

1,  Fact  of  transportation.  —  It  has   been    stated   that   the 
massive  mountains  have  been  eroded  into  ridges  and  valleys 
by  running  w.ater.     The  material  worn  out  has  been  trans- 
ported somewhere  by  the  same  waters. 

Part  of  the  transported  material  in  all  such  operations 
goes  to  form  the  great  alluvial  plains  that  occupy  the  river- 
valleys  throughout  their  course.  Part  is  carried  on  to  the  sea 
into  which  the  river  empties,  where  it  meets  the  counteracting 
waves  and  currents  and  is  distributed  for  the  most  part  along 
the  shores,  filling  estuaries  or  bays,  or  making  deltas,  and  ex- 
tending the  bounds  of  the  land. 

Thus  the  mountains  of  a  continent  are  ever  on  the  move 
seaward,  and  contribute  to  the  enlargement  of  the  sea-shore 
plains.  The  continent  is  losing  annually  in  mean  height,  but 
gaining  in  width,  or  extent  of  dry  land. 

2,  Transporting  power  of  water.  —  The  transporting  power 
of   running  water   is  very   great    when    the   flow  is    rapid. 
Large   stones  and  masses  of   rocks  are  torn  up  and  moved 
onward  by  the  mountain- torrent.      It  has  been  calculated, 
after  some  trials,  that  a  current  of  four  miles  an  hour  will 
carry  stones  2-J-  inches  in  diameter ;  of  two  miles,  pebbles  of 
0.6  inch  ;  of  two  thirds  of  a  mile,  fine  sand,  about  .064  in 
diameter ;    of  one  third   of   a   mile,   fine  earth  or   clay,  the 
particles  .016  in  diameter;  the  mean  diameter  of  the  largest 
transportable  particles  varying  as    the  square  of  the  velocity, 
supposing  them  of  like  density. 

Hence,  as  a  stream  loses  in  velocity  it  leaves  behind  the 
coarser  material,  and  carries  only  the  finer ;  if  the  rate  be- 
comes very  slow,  it  drops  the  gravel  or  the  sand,  and  bears 
on  only  the  finest  earth  or  clay.  Consequently,  where  the 


WATER.  99 

current  is  swift,  the  bottom  (and  the  shore  also,  wherever  the 
current  strikes  it)  is  stony  or  pebbly ;  and  where  the  water 
is  still,  or  nearly  so,  the  bottom  and  shores  are  muddy. 

3.  Amount  of  material  transported.  —  The  amount  of  trans- 
ported material  varies  with  the  size  and  current  of  the  rivers 
and  the  kind  of  country  they  flow  through.     The  Mississippi 
carries  annually  to  the  Gulf  of  Mexico,  according  to  Hum- 
phreys and  Abbot,  on  an  average,  812,500,000,000  pounds  of 
silt,  —  equal  to  a  mass  one  square  mile  in  area  and  241  feet 
deep,  —  and  its  bottom  waters  push  on  enough  more  to  make 
the  241  feet  268  feet.     The  process  slowly  lowers  the  drain- 
age area  of   the   river,  and  the  mean  amount   of   lowering 
indicated  by  the  facts   stated   is   one  foot  in  4,920  years. 
The  total  annual  discharge  of  silt  by  the  GangeJTtfas r  been 
estimated  at  6,368,000,000  cubic  feet. 

Besides  the  silt,  rivers  carry  what  the  waters  _ta_ke_  into 
solution.  The  amount  is  generally  between  a  third  and  a  half 
of  that  mechanically" 'transported ;  but  sometimes  nearly  an" 
e^uaJjgeignt.  If  one  Tialf,  in  the  case  of  the  Mississippi, 
the  interval  4,920  years  becomes  3,280.  The  salts  held  in 
solution  are  often  about  one  half  calcium  carbonate,  and  the 
rest  calcium  sulphate,  sodium  chloride  (common  salt),  and 
magnesian  and  potash  salts,  with  traces  of  silica  and  other 
ingredients.  The  contributions  of  these  salts  from  rivers 
to  the  ocean  must  be  making  a  slow  increase  of  its  saltness. 
In  some  cases  the  rivers  carry  the  salts  to  inland  seas  or 
plains,  which  have  no  drainage  toward  the  ocean,  and  which 
therefore  are  saline.  Besides,  arid  plains  become  saline 
because  of  the  capillary  action  which  brings  moisture  from 
below  to  the  surface,  as  evaporation  goes  on  above  depositing 
the  contained  saline  ingredients,  such  as  the  sodium  chloride, 
sodium  carbonate,  and  magnesian  salts  of  such  places. 

4.  Alluvial  or  Fluvial  formations.  —  The  deposits  made  by 
the  transported  material  which  now  constitute  the   alluvial 
plains  of  the  river-valleys  cover  a  large  part  of  a  continent, 
since   rivers  or  smaller   streams  are   almost  everywhere  at 


100  DYNAMICAL  GEOLOGY. 

work.  They  are  made  up  of  layers  of  pebbles  or  gravel,  and 
of  earth,  silt,  or  clay,  especially  of  these  finer  materials. 
Logs,  leaves,  shells,  and  bones  occur  in  them :  but  these  are 
rare  ;  for  whatever  floats  down  stream  is  widely  scattered  by 
the  waters,  and  to  a  great  extent  destroyed  by  wear  and  decay. 
The  level  of  the  alluvial  plain  is  ordinarily  that  of  the  level 
of  the  higher  floods,  and  hence  the  name  of  'flood-plain  often 
applied  to  it.  The  spreading  waters,  by  here  losing  their 
velocity,  owing  to  friction,  built  up  the  deposits.  The  river 
margin  is  often  a  little  above  flood-level. 

5.  Terraces.  —  Eiver- valley  or  fluvial  formations  are  often 
in  terraces.      The  terraces  are  in  general  a  consequence  of 
floods  far  higher  than  ordinary  floods  (like  those  after  the 
Glacial  era,  page  355),  their  plains   being  true  flood-plains. 
But   some   terraces   have   been    formed  by  the  abrasion  of 
higher  terraces.     Others,  on  bays,  are  alluvial  flats  left  high, 
after  a  change  of  level ;  and  sea-shore  flats  and  beaches,  and 
horizontal  lines  of  wave-erosion   on  cliffs,  have   often  been 
left  high  in  the  same  movements. 

6.  Estuary   and   Delta   formations.  —  The   detritus-material 
discharged  by  the  river  at  its  mouth  tends  to  fill  up  the 
bay   into  which   it   empties,    and   make   wide   flats    on    its 
borders,  and  thus  contract  it  to  the  breadth  merely  of  the 
river-current. 

Where  the  tides  are  feeble  and  the  river  large,  the  deposits 
about  the  mouth  of  the  stream  gradually  encroach  on  the 
ocean,  and  make  great  plains  and  marshy  flats,  which  are 
intersected  by  the  many  mouths  of  the  river  and  a  network 
of  cross-channels.  Such  a  formation  is  called  a  delta.  Fig. 
107  represents  the  delta  of  the  Mississippi,  the  white  lines 
being  the  water-channels  and  the  black  the  great  alluvial 
plains.  The  delta  properly  commences  below  the  mouth  of 
Eed  Eiver,  where  the  Atchafalaya  lay  on,  or  side-channel  of 
the  river,  begins.  The  whole  area  is  about  12,300  square 
miles  ;  about  one  third  is  a  sea  marsh,  only  two  thirds  lying 
above  the  level  of  the  Gulf. 


WATER. 


101 


The  deltas  of  the  Nile,  Ganges,  and  Amazon  are  similar  in 
general  features  to  the  delta  of  the  Mississippi. 

The  detritus  poured  into  the  ocean  where  the  tides  or  cur- 
rents are  strong,  and  a  considerable  part  of  that  where  the 


tides  are  feeble,  goes  to  form  sea-shore  flats  and  sand-banks 
and  off-shore  deposits.  In  their  formation  the  ocean  takes 
part  through  its  waves  and  currents,  and  hence  they  are 


102  DYNAMICAL  GEOLOGY. 

more  conveniently  described  in  connection  with  the  remarks 
on  oceanic  action. 


B.    Subterranean  Waters. 

1.  Origin  and  course  of  subterranean  waters.  —  A  part  of  the 
waters  that  fall  on  the  earth's  surface  —  on  its  mountains 
as  well  as  its  plains  —  sinks  through  the  ground  and  into 
the  rocks  beneath,  wherever  there  are  openings  or  crevices, 
or  looseness  of  texture,  and  thus  becomes  subterranean. 
The  waters  usually  pass  easily  through  sandstones ;  but 
over  a  clayey  or  other  compact  stratum  they  accumulate, 
and  often  make  wet  springy  soil  above ;  or  if  the  stratum 
is  inclined,  they  may  descend  to  great  depths,  or  come 
to  the  light  again  wherever  it  outcrops  at  a  lower  level. 
The  descending  waters  sometimes  gather  into  subterranean 
streams,  which  have  powers  of  abrasion.  Over  large  areas 
in  some  limestone  regions,  and  many  volcanic,  surface  streams 
are  wanting,  because  of  the  cavernous  recesses ;  the  waters 
carry  on  an  underground  system  of  drainage.  Thus  come 
springs,  subterranean  streams  large  and  small,  and  copious 
out-flows  beneath  the  sea-level  along  coasts. 

A  region  of  horizontal  limestone  abounds  in  sink-holes,  as 
well  as  caverns  ;  and  sometimes  rivers  plunge  down  the 
openings  into  the  recesses  below,  and  are  lost,  or  emerge 
again  in  fuller  flow  a  mile  or  more  away. 

Ordinary  waters  easily  erode  limestone,  because  they  con- 
tain carbonic  acid  (page  83).  Through  the  joints  or  fissures 
the  waters  find  a  way  downward,  and  the  erosion  they  pro- 
duce makes  and  widens  the  joints,  forming  often  funnel- 
shaped  sink-holes.  At  the  bottom  of  the  sink-hole  the 
waters  work  laterally,  eroding  channels  and  chambers,  in 
long  series  and  varying  directions ;  and  if,  later,  they  suc- 
ceed in  penetrating  to  a  still  lower  level,  another  tier  of 
chambers  is  begun.  Undermining  also  goes  on,  causing  falls 
of  rock,  and  sometimes  large  enough  to  make  feeble  earth- 


WATER. 


103 


quakes;    and   thus   the  chambers   become   high  and   large. 
Occasionally  the  roof  for  an  interval  caves  in,  and  the  cavern, 


Fig.  108. 


MAMMOTH  CAVE. 


with  the  river  enclosed,  becomes  open  to  the  light,  and  is 
then  an  example  of  one  method  of  making  limestone  gorges. 


104  DYNAMICAL  GEOLOGY. 

The  preceding  map  (reduced  from  H.  C.  Hovey's  interesting 
work  on  American  Caverns)  represents  the  passages  and 
chambers  of  Mammoth  Cave,  Kentucky.  This  cave  occu- 
pies, with  its  windings,  an  area  of  several  square  miles  in 
the  Carboniferous  limestone.  The  length  of  the  caverns  in 
this  limestone  in  Kentucky  (a  rock  200  to  1000  feet  thick)  is 
estimated  by  Prof.  Shaler  at  100,000  miles.  Luray  Cavern, 
in  Luray  Valley,  Virginia,  is  comparatively  small,  -but,  as 
described  by  Mr.  Hovey,  it  is  one  of  the  most  remarkable  in 
the  world,  for  the  beauty  of  its  stalactitic  hangings  and  the 
grandeur  of  its  subterranean  chambers. 

In  many  caverns,  bones  of  the  animals  that  have  inhabited 
them,  including  sometimes  those  of  Man  with  his  imple- 
ments of  stone  or  shell  or  other  material,  are  found  buried 
beneath  or  within  the  stalagmite  that  covers  the  floor — the 
perpetual  dripping  keeping  up  its  constant  deposition  (pages 
37  and  85.) 

Caves  exist  in  the  elevated  coral  reefs  of  the  Pacific,  which 
are  certainly  of  comparatively  recent  origin.  One,  on  the 
island  of  Atiu,  near  Tahiti,  has  "  interminable  windings  "  and 
many  chambers,  "with  fretwork  ceilings  of  stalactite  and 
stalagmite  "  ( J.  Williams).  There  are  others  on  Oahu,  which 
give  a  passage  to  island  streams. 

The  erosion  is  helped  forward  (1)  by  the  oxidation  of 
pyrite  (page  82)  where  it  is  present,  the  resulting  sul- 
phuric acid  turning  limestone  into  gypsum ;  and  also  (2)  by 
the  formation  of  nitric  acid  from  the  nitrogen  of  the  air, 
which  erodes  the  limestone,  making  calcium  nitrate.  The 
caves  of  Kentucky  and  Indiana  have  afforded  a  large  amount 
of  this  nitrate  for  the  making  of  nitre. 

Subterranean  waters  often  become  miner cd  waters.  They 
are  made  calcareous  by  limestones  along  their  course ;  saline, 
from  the  saline  ingredients  of  rocks ;  sulphureous,  by  decom- 
posing iron  sulphides ;  carbonated,  by  any  acid,  as  sulphuric, 
attacking  a  limestone  and  setting  carbonic  acid  free ;  chaly- 
beate, if  iron  is  present  in  the  last  process ;  and  magnesian,  or 


ARTESIAN  WELLS. 


105 


of  other  quality,  in  connection  with  the  last,  when  the  decom- 
position of  any  rock  is  going  forward  that  can  afford  the 
materials,  and  when  the  ocean  is  a  source.  They  may  be- 
come warm  waters  through  the  decomposition  of  pyrite,  etc., 
or  through  subterranean  heat,  and  may  receive  vapors  and 
various  mineral  materials  from  the  depths  below. 

2.  Artesian  Wells. — When  strata  are  inclined,  and  water 
descends  along  one  of  the  layers  between  others  that  are 
sufficiently  close  to  confine  it,  the  pressure  increases  with  the 
descent ;  so  that  the  water  will  rise  through  a  boring  made 
down  to  it,  and  sometimes  F.     1Qg 

in  a  high  jet.    The  principle     ..fr~~  **  a 

is  illustrated  in  Fig.  109,  I 
in  which  a  b  is  the  water- 
bearing stratum,  I  c  the 
boring,  and  e  b  the  amount 
of  descent.  The  height  of 
the  jet  falls  much  short  of 
I  c,  on  account  chiefly  of  the 
underground  friction. 

Such  wells  are  called  Artesian  wdls  or  borings,  from  the 
district  of  Artois  in  France,  where  they  were  early  made. 
'The  Artesian  well  of  Grenelle  in  Paris  is  1,798  feet  deep,  and 
when  first  made  the  water  dartsd  out  to  a  height  of  112  feet. 
One  at  St.  Louis  has  a  depth  of  3,843-J-  feet,  but  without  get- 
ting water,  because  the  region  for  many  miles  around  is  one 
of  horizontal  rocks.  Such  wells  are  made  for  agricultural 
and  manufacturing  purposes  in  many  dry  regions,  and  they 
have  proved  successful  even  in  Sahara. 

3.  Land-Slides. —  Land-Slides  are  of  different  kinds  :  — 

1.  The  sliding  of  the  surface  earth,  or  gravel,  of  a  hill  down 
to  the  plain  below.     This  effect  may  be  caused  by  the  waters 
of  a  severe  storm  wetting  the  material  deeply  and  giving  it 
greatly  increased  weight,  besides  loosening  its  attachment  to 
the  more  solid  mass  below. 

2.  The  sliding  down  a  declivity  to  the  plain  below  of  the 


Section  illustrating  the  origin  of  Artesian  wells. 


106  DYNAMICAL  GEOLOGY. 

upper  layer  of  a  rock-formation.  This  may  happen  when  this 
upper  layer  rests  on  a  clayey  or  sandy  layer  and  the  latter 
becomes  very  wet  and  greatly  softened  by  the  waters ;  the 
upper  layer  slides  down  on  the  softened  bed. 

3.  The  settling  of  the  ground  over  a  large  area.  This  may 
take  place  when  a  layer  of  clay  or  loose  sand  becomes  wet 
and  softened  by  percolating  waters,  and  then  is  pressed  out 
laterally  by  the  weight  of  the  superincumbent  layers.  But 
such  a  result  is  not  possible  unless  there  is  a  chance  for  the 
wet  layer  to  move  or  escape  laterally.  Sometimes  part  of  a 
wet  clayey  layer,  pressed  to  one  side  in  this  way,  is  left  very 
much  folded,  while  the  associated  sandy  layers  have  their 
usual  regular  bedding. 

2.  The  Ocean. 

The  ocean  is  vast  in  extent  and  vast  in  the  power  which 
it  may  exert.  But  its  mechanical  work  in  Geology  is  mostly 
confined  to  its  coasts  and  to  soundings,  where  alone  material 
exists  in  quantity  within  reach  of  the  waves  or  currents.  In 
ancient  time,  when  the  continents  had  not  their  present 
mountains,  and  were  to  a  great  extent  submerged  at  shallow 
depths,  this  work  was  performed  simultaneously  over  a  large 
part  of  their  surface,  and  strata  nearly  of  continental  area 
were  sometimes  formed.  In  the  present  age,  oceanic  action 
is  almost  wholly  confined  to  the  borders  of  the  continents. 

The  saltness  of  the  ocean  gives  it  a  density  of  1.0245  to 

1.0278,  that  of   pure  fresh  water  being  1.      It  is  slightly 

I    the  greatest  in  the  tropics,  because  of  the  evaporation.     A 

cubic  foot  weighs  about  64  pounds.     There  are  three  cou- 

1   sequences  of  the  saltness:    (1)  greater  transporting  power 

I  than  fresh  water,  on  account  of  its  density ;  (2)  much  quicker 

\  deposition  of  sediment,  the  time  required  in  salt  water  being 

\a  fifteenth  of  that  in  fresh,  on  account  of  the  less  adhesion  of 

ithe  particles ;  (3)  a  supply  of  common  salt  and  magnesian 

baits,  etc.,  for  making  deposits  of  salts,  and  for  use  in  chem- 


WORK  OF  THE  OCEAN.  107 

ical  changes  attending  the  making  of  rocks  and  minerals,  it 
being  the  largest  of  mineral  springs  (p.  28). 

The  mechanical  effects  of  the  ocean  are  produced  by  its 
waves  and  currents. 


I.    Erosion   and   Transportation. 

1.  Waves,  —  7.  General  action.  —  The  force  in  oceanic  waves 
is  a  constant  force.     Night  and  day,  year  in  and  year  out, 
with  hardly  an  intermission,  they  break  against  the  beaches 
and  rocks  of  the  coast ;  sometimes  gently,  sometimes  in  heavy, 
plunges  that  have  the  force  of  a  Niagara  of  almost  unlimited 
breadth.    The  gentlest  movements  have  some  grinding  action 
among  the  sands,  while  the  heaviest  may  dislodge  and  move 
along,  up  the  shores,  rocks  many  tons  in  weight.     Niagara 
wastes  its  power  by  falling  into  an  abyss  of  waters :  while 
in  the  case  of  the  waves  the  rocks  are  bared  anew  for  each 
successive  plunge.     The  waters  are  often  loaded  with  gravel 
and  sand  when  they  strike,  and   thus  carry  on  abrasion. 
Cliffs  are  undermined,  rocks  are  worn  to  pebbles  and  sand, 
and,  through  mutual  friction,  sand  is  ground  to  the  finest 
powder.    Eocky  headlands  on  windward  coasts  are  especially 
exposed  to  wear,  since  they  are  open  to  the  battering  force 
from  different  directions. 

2.  Level  of  greatest  eroding  action.  —  The  eroding  action  is 
greatest  for  a  short  distance  above  the  height  of  half- tide, 
and,  except   in   violent   storms, 

it  is  almost  null  below  low- 
tide  level.  Fig.  110  represents 
in  profile  a  cliff,  having  its  lower 
layers,near  the  level  of  low  tide, 
extending  out  as  a  platform  a  11 
hundred  yards  wide.  As  the  cuff,  New  south  wales, 

tide  commences  to  move  in,  the 

waters,  while  still  quiet,  swell  over  and  cover  this  platform, 
and  so  give  it  their  protection ;  and  the  force  of  wave-action, 


108  DYNAMICAL   GEOLOGY. 

which  is  greatest  above  half-tide,  is  mainly  expended  near 
the  base  of  the  cliff,  just  above  the  level  of  the  platform. 
But  for  much  battering  effect  a  coast  should  be  shelving,  so 
as  to  raise  the  waters  as  they  advance.  If  deep  alongside  of 
a  cliff,  there  is  simply  a  rise  and  fall,  with  little  abrasion. 

3.  Action  landward.  — Waves  on  shallow  soundings   have 
some  transporting  power ;  and,  as  they  always  move  toward 
the  land,  their  action  is  landward.     They  thus  beat  back, 
little  by  little,  any  detritus  in  the  waters,  preventing  that  loss 
to  continents  or  islands  which  would  take  place  if  it  were  cai  - 
ried  out  to  sea. 

4.  Effect  on  the  outline  of  coasis ;   No  excavation  of  narrow 
valleys.  —  As  the  action  of  waves  on  a  coast  tends  to  wear 
away  headlands,  and  at  the  same  time  to  fill  up  bays  with 
detritus,  it  usually  results  in  making  the  outline  more  regular 
or  even.     There  is  nowhere  a  tendency  to  excavate  narrow 
valleys  into  a  coast,  like  those  occupied  by  rivers.     Such 
valleys  are  made  by  the  waters  of  the  land ;  for  the  ocean 
can  work  at  valley-making  only  when  it  has  already  an  open 
channel  for  the  waters  to  pass  through,  and  then  the  valleys 
are  of  very  great  width.     If  a  continent  were  sinking  slowly 
in  the  ocean,  or  rising  slowly  from  it,  wave-action  would  still 
be  attended  by  the  same  results ;  for  each  part  of  the  surface 
would  be 'successively  a  coast-line,  and  over  each  there  would 
be  the  same  wearing  away  of  headlands  and  filling  of  bays, 
instead  of  the  excavation  of  valleys. 

2.  Tidal  currents. — Tidal  currents  often  have  great  strength 
when  the  tide  moves  through  channels  or  among  islands,  and 
then  they  are  a  means  of  erosion  and  transportation  daily  in 
action,  wherever  there  is  rock,  mud,  or  sand  within  their 
reach. 

The  out-flowing  current  from  bays,  or  that  connected  with 
the  ebbing  tide,  is  deeper  in  its  action,  and  has,  therefore, 
more  excavating  and  more  transporting  power  than  the  in- 
flowing, or  that  of  the  incoming  tide.  The  latter  moves  on 
as  a  great  swelling  wave,  and  fills  the  bays  much  above  their 


WORK  OF  THE  OCEAN.  109 

natural  level ;  but  the  out-flowing  current  begins  along  the 
bottom  before  the  tide  is  wholly  in,  owing  to  the  accumula- 
tion of  waters,  and  when  the  tide  changes  it  adds  to  the 
strong  current-movement  already  in  progress. 

The  piling  up  of  the  waters  in  a  bay  by  the  tides,  or  by 
storms,  produces,  especially  if  the  entrance  is  not  very  broad, 
a  strong  out-flowing  current  at  bottom,  which  tends  to  keep 
the  channel  deep  and  clear  of  obstructions. 

The  in-flowing  tide,  sweeping  along  a  coast,  checks  partly 
or  wholly  the  outflow  of  the  rivers.  This  causes  a  deposition 
of  more  or  less  of  the  detritus  which  the  rivers  transport,  near 
or  against  the  shores  or  flats  just  beyond  the  river-channel ; 
and  thus  it  often  makes  great  sand-flats,  which  encroach 
on  the  entrance.  If  a  long  point  projects  on  the  side  of  the 
mouth  first  reached  by  the  in -flowing  tide,  the  tidal  flow  may 
carry  the  detritus  far  beyond  the  river's  mouth;  but  if  no 
such  point  exists,  and  the  opposite  cape  is  the  longer,  the 
detritus  will  be  thrown  into  the  throat  of  the  stream,  and 
the  entrance  become  more  or  less  choked.  The  river  mouths 
of  the  Connecticut  shore,  on  the  north  side  of  Long  Island 
Sound,  along  which  the  in-flowing  tide  moves  westward,  illus- 
trate well  these  facts.  The  two  largest  of  the  rivers,  the 
Connecticut  and  Housa tonic,  are  of  the  unfortunate  kind,  as 
they  have  no  eastern  cape,  while  New  Haven,  having  only 
very  small  streams,  is  much  better  off,  as  regards  depth  of 
water  for  entrance,  because  of  a  projecting  eastern  cape. 

The  bore  or  eagre  of  some  great  rivers  is  a  kind  of  tidal 
flow  up  a  stream.  It  is  produced  when  the  regular  rise  of 
the  tide  in  the  bay  at  the  mouth  of  the  river  is  obstructed 
by  the  form  of  the  entrance  and  its  sand-banks,  together  with 
the  outflow  of  the  river,  so  that  the  waters  are  for  a  while 
prevented  from  entering,  until,  finally,  all  those  of  one  tide 
rush  in  at  once,  or  in  a  few  great  waves.  The  eagres  of  the 
Amazon,  the  Hoogly  in  India  (one  of  the  mouths  of  the 
Ganges),  and  the  Tsien-tang  in  China,  are  among  the  most 
remarkable.  In  the  case  of  the  Tsien-tang,  the  water  moves 


110  DYNAMICAL  GEOLOGY. 

up  stream  in  one  great  wave,  plunging  like  an  advancing 
cataract,  four  or  five  miles  broad  and  30  feet  high,  at  a  rate 
of  25  miles  an  hour.  The  boats  in  the  middle  of  the  stream 
simply  rise  and  fall  with  the  passage  of  the  wave,  being 
pushed  forward  only  a  short  distance ;  but  along  the  shores 
there  is  often  great  devastation,  the  banks  being  worn  away 
and  animals  sometimes  surprised  and  destroyed. 

3.  Currents  made  by  winds.  —  There  are  also  currents  pro- 
duced  by  winds,  especially  when  there  are  long  storms,  or 
when  the  winds  blow  for  months  in  one  direction.  The  great 
currents  of  the  oceans,  such  as  the  Gulf  Stream,  are  attributed 
by  some  physicists  to  this  source.  Such  currents,  sweeping 
by  a  coast,  transport  from  one  place  to  another  in  their  course 
more  or  less  of  the  sand  of  the  shores,  often  making  long 
sand-flats  or  spits  off  the  shores  to  leeward,  as  on  the  south 
coast  of  Long  Island  and  the  more  southern  parts  of  the 
Atlantic  border.  The  action  is  aided  by  the  tidal  currents. 
In  some  cases  the  drifted  sand  may  be  in  part  carried  back 
again  when  the  season  changes  to  that  in  which  the  wind 
blows  from  the  opposite  direction.  Other  portions  of  detri- 
tus may  be  carried  by  them  away  from  the  land  and  distri- 
buted in  the  deeper  waters. 

The  great  currents  of  the  ocean  are  for  the  most  part  so 
distant  from  the  borders  of  the  continents  that  little  detri- 
tus comes  within  their  reach.  As  these  currents  have  great 
depth,  —  often  a  thousand  feet  or  more,  —  their  course  is 
determined  partly  by  the  deep-water  slopes  of  the  submerged 
border  of  a  continent,  so  that  when  the  border  is  shallow 
for  a  long  distance  out  (as  off  New  Jersey  and  Virginia,  where 
this  long  distance  is  even  50  to  80  miles),  the  main  body  of 
the  current  is  equally  remote.  Wherever  it  actually  sweeps 
close  along  a  coast,  it  may  bear  away  some  detritus  to  drop  it 
over  the  bottom  in  the  neighboring  waters.  The  flow  of  the 
Gulf  Stream  against  the  submerged  slope  of  the  oceanic  basin 
(about  three-fourths  of  a  mile  per  hour)  is  sufficient  to  keep 
the  bottom  free  from  loose  detritus.  Verrill  has  suggested 


WORK   OF   THE  OCEAN.  Ill 

that  the  burrowing  of  fishes  for  food  aids,  by  loosening  the 
material. 

The  oceanic  currents  flowing  from  polar  seas  produce  im- 
portant effects  by  means  of  the  icebergs  which  they  bear  into 
warmer  latitudes.  These  icebergs  are  sometimes  freighted 
with  earth  and  rocks;  and  wherever  they  melt,  they  drop 
all  to  the  ocean's  bottom.  The  sea  about  the  Newfound- 
land banks  is  one  of  the  regions  of  the  melting  icebergs  ; 
and  there  is  no  doubt  that  vast  submarine  accumulations 
of  such  material  have  been  there  made  by  this  means.  It 
has  been  suggested  that  the  banks  may  have  been  thus 
formed. 


2.   Distribution  of   material,  and  the  formation  of  marine 
and  fluvio-marine  deposits. 

1.  Origin  of  material. — The  material  used  by  the  waves 
and  currents  is  either  —  (1)  the  stones,  gravel,  sand,  clay,  or 
earth  produced  by  the  wear  of  coasts ;  or  (2)  the  detritus 
brought  down  by  rivers  and  poured  into  the  ocean,  as  ex- 
plained on  page  98. 

The  latter,  in  the  present  age,  is  vastly  the  most  important. 
But  in  the  earlier  geological  ages,  when  the  dry  land  was  of 
small  extent,  rivers  were  small  and  were  but  a  feeble  agency. 
The  ocean  had  then  vastly  greater  advantages  than  now,  be- 
cause, as  stated  on  page  106,  the  continents  were  mostly  sub- 
merged at  shallow  depths,  or  lay  near  tide-level  within  reach 
of  the  waves  and  currents. 

The  decomposition  or  disintegration  of  exposed  rocks 
through  the  agency  of  air  and  moisture  must  have  aided  in 
degradation  formerly  more  than  now,  since  in  Paleozoic  time 
and  earlier,  carbonic  acid  gas,  the  chief  agent  of  destruction, 
was  much  more  abundant  in  the  atmosphere  than  it  is  now. 
This  agent  is  carried  to  the  earth's  surface  by  the  rains,  and 
it  is  still  effective  in  the  decomposition  of  granite,  gneiss,  and 
many  other  rocks. 


112  DYNAMICAL  GEOLOGY. 

2.  Forces  in  action.  —  In  the  distribution  of  the  material, 
the  waves  and  marine  currents  have  either  worked  alone,  in 
the  manner  explained  on  the  preceding  pages,  or  in  conjunc- 
tion with  river-currents  wherever  these  existed. 

3.  Marine  formations,  —  The  marine  formations  are  of  the 
following  kinds :  — 

Beach-accumulations.  —  Beaches  are  made  of  the  material 
borne  up  the  shores  by  the  waves  and  tides  and  left  above 
low-tide  level.  This  material  consists  of  stones  or  pebbles, 
sand,  mud,  -earth,  or  clay.  It  is  coarse  where  the  waves  break 
heavily,  because,  although  trituration  to  powder  is  going  on 
at  all  times,  the  powerful  wave-action  and  the  undercurrent 
carry  off  the  finer  material  into  the  off-shore  shallow  waters," 
where  it  settles  over  the  bottom  or  is  distributed  by  currents. 
It  is  fine  where  the  waves  are  gentle  in  movement,  as  in  shel- 
tered bays,  or  estuaries,  the  triturated  material  remaining  in 
such  places  near  where  it  is  made,  and  often  being  the  finest 
of  mud. 

Sand-banks,  or  reefs ;  Shallow-water  accumulations.  —  Shal- 
low-water accumulations  may  be  produced  in  bays,  estuaries, 
or  the  inner  channels  of  a  coast,  and  over  the  bottom  outside. 
They  consist  usually  of  coarse  or  fine  sand  and  earthy  de- 
tritus, but  may  include  pebbles  or  stones  when  the  currents 
are  strong.  The  material  constituting  them  is  derived  from 
the  land  through  the  wearing  and  transporting  action  either 
of  the  waves  and  currents,  or  of  rivers.  The  accumulations 
may  increase  under  wave-action  in  shallow  water,  until  they 
approach  or  rise  above  low-tide  level,  and  then  they  form 
sand-banks.  Such  sand-banks  keep  their  place  in  the  faco 
of  the  waves,  for  the  same  reason  as  the  platform  of  rock 
mentioned  on  page  107  and  illustrated  in  Fig.  110. 

Fluvio-marine  formations.  —  Most  of  the  accumulations  in 
progress  on  existing  shores,  whether  sand-banks,  or  estuary, 
or  off-shore  deposits,  especially  about  well-watered  continents, 
contain  more  or  less  of  river-detritus,  and  are  modified  in 
their  forms  by  the  action  of  river-currents.  Along  the  whole 


WORK  OF   THE   OCEAN.  113 

eastern  coast  of  the  United  States  south  of  New  England, 
and  on  all  the  borders  of  the  Gulf  of  Mexico,  the  formations 
in  progress  are  mainly  flumo-marine,  —  that  is,  the  combined 
result  of  rivers  and  the  ocean.  The  coast-region  on  the  con- 
tinent is  now  slowly  widening  through  this  means,  and  has 
been  widening  for  an  indefinite  period :  This  coast-region  is 
low,  flat,  often  marshy,  full  of  channels  or  sounds  ;  and  facing 
the  ocean  there  is  a  barrier-reef,  made  of  sand. 

The  rivers  pour  out  their  detritus  especially  during  their 
floods,  and  the  ocean's  waves  and  currents  meet  it  as  the  tide 
sets  in,  with  a  counter-action,  or  one  from  the  sea, ward ;  and 
between  the  two  the  waters,  as  they  lose  their  velocity,  drop 
the  detritus  over  the  bottom.  When  the  river  is  very  large 
and  the  tides  feeble,  the  banks  and  reefs  extend  far  out 
to  sea.  The  Mississippi  thus  stretches  its  many-branched 
mouth  (page  101)  fifty  miles  into  the  Gulf.  When  the  tide 
is  high,  sand-bars  are  formed  ;  and  the  higher  the  tides  the 
closer  are  the  sand-bars  to  the  coast.  When  the  stream  is 
small,  the  ocean  may  throw  a  sand-bank  quite  across  its 
mouth,  so  that  there  may  be  no  egress  to  the  river-waters  ex- 
cept by  percolation  through  the  sand,  or,  if  a  channel  is  left 
open,  it  may  be  only  a  shallow  one. 

3.  Structure  of  the  formations. 

Beach-formations  are  very  irregular  in  stratification  in  their 
upper  portions,  where  they  are  made  by  the  toss  of  the  waves 
combined  with  drifting  by  the  winds.  The  layers  —  as  shown 
in  Fig.  22  d,  page  45  —  have  but  little  lateral  extent,  and 
change  in  character  every  few  feet.  But  the  sloping  part 
swept  by  the  waves  below  high-tide  level  is  very  evenly 
stratified  parallel  to  .  the  surface ;  and  since  this  surface 
pitches  at  an  angle  usually  of  5°  to  15°,  the  beach-made 
beds  have  the  same  pitch  or  dip.  The  coarser  beaches  have 
the  highest  slopes. 

The  sand-banks  and  reefs  made  in  shallow  waters  along  a 

8  . 


114  DYNAMICAL     GEOLOGY. 

coast  have  a  regular  and  more  horizontal  stratification,  and 
are  mostly  composed  of  sand  with  some  beds  of  pebbles. 
They  often  vary  much  every  mile  or  every  few  miles.  The 
extent  and  regularity  of  level  of  the  submerged  area  off  a, 
coast  will  determine  in  a  great  degree  the  extent  to  which 
the  uniformity  of  stratification  may  extend ;  and  in  this 
respect  the  former  geological  ages,  as  observed  on  page  106, 
had  greatly  the  advantage  of  the  present. 

Ripple-marks  (Fig.  24,  page  46)  are  made  by  the  wash  of 
the  waters  over  a  sand-flat  or  up  a  beach,  or  over  the  bottom 
within  soundings ;  also  by  wave-action  where  the  waters  are 
not  flowing.  JRill-m-arJcs  (Fig.  25)  are  produced  when  the 
return  waters  of  a  tide,  or  of  a  wave  that  has  broken  on  a 
beach,  flow  by  an  obstacle,  as  a  shell  or  pebble,  and  are  piled 
up  a  little  by  it  so  as  to  be  made  to  plunge  over  it,  and  so 
erode  the  sands  for  a  short  distance  below  the  obstacle.  The 
cross-bedded  structure  results  from  the  rapid  inward  move- 
ment of  the  tide,  or  the  flow  of  any  current,  over  a  sandy 
bottom:  it  makes  a  series  of  inclined  layers  by  the  piling 
action  dipping  in  the  direction  of  the  movement ;  when  the 
movement  ceases,  the  detritus  may  deposit  horizontally  for  a 
while ;  and  afterward  the  flow  and  its  results  may  be  repeated. 
When  there  are  plunging  waves  accompanying  the  rapid  flow 
of  a  current,  the  obliquely  laminated  layer  is  broken  up  into 
short  wave-like  parts,  —  as  in  the  flow-and-plunge  structure 
(page  45). 

The  imbedded  shells  and  other  animal  relics  in  a  beach  are 
commonly  broken ;  those  in  the  bays  or  off-shore  shallow 
waters  out  of  the  reach  of  the  waves  may  be  unbroken,  or  may 
lie  as  they  did  when  living ;  but  if  the  waters  are  not  so  deep 
but  that  the  shells  or  corals  are  exposed  to  wave-action,  they 
may  be  broken  or  worn  to  powder,  and  enter  in  this  state  into 
the  formation  in  progress.  (See  further,  page  79,  the  remarks 
on  the  formation  of  limestone  from  shells  or  corals.) 

Deposits  of  broken  shells  under  water  are  sometimes 
made  by  fishes  that  have  ta,keu  tbe  animals  for  food.  Such 


FREEZING  AND  FROZEN  WATERS.  115 

beds  made  by  fishes  answer  to  the  shell-heaps  of   human 
origin. 

In  the  sands  of  beaches  near  low-tide  level,  borings  of  Sea- 
worms,  or  of  some  Mollusks  or  Crustaceans,  may  exist. 


3.  Freezing  and  Frozen  Waters. 

A.  Freezing  Water. 

As  water  in  the  act  of  freezing  expands  after  reaching 
39°  *2  F.  (4°  C.),  freezing  in  the  seams  of  rock  opens  the  seams 
and  tears  masses  asunder.  The  expansion  on  reaching  32°  F. 
is  l-35th  lineally,  and  the  density  is  diminished  to  0*92. 
The  results  of  expansion  are  most  marked  in  rocks  that  are 
much  fissured,  or  intersected  by  joints,  or  that  have  a  slaty 
or  laminated  structure.  As  the  action  continues  through 
successive  years  and  centuries,  it  often  results  in  great  accu- 
mulations of  broken  stone.  The  slope,  or  talus,  of  fragments 
at  the  foot  of  bluffs  of  trap  or  basalt  is  often  half  as  high 
as  the  bluff  itself.  In  tropical  countries,  bluffs  have  no  such 
masses  of  ruins  at  their  base. 

Granular  rocks,  whether  crystalline  or  not,  when  they  read- 
ily absorb  water,  lose  their  surface-grains  by  the  same  freez- 
ing process.  Granite,  as  well  as  porous  sandstones,  may  thus 
be  imperceptibly  turning  to  dust,  earth,  or  gravel.  In  Alpine 
regions  this  action  may  be  incessant. 

Alternate  freezing  and  thawing  produces  (as  explained 
by  Kerr)  a  movement  of  earth  and  gravel  on  slopes,  with 
re-arrangements  of  the  materials. 

B.  Frozen  Water. 

The  effects  of  ice  and  snow  are  conveniently  considered 
under  three  heads:  1.  The  ice  of  Lakes  and  rivers;  2.  Gla- 
ciers; 3.  Icebergs. 


116  DYNAMICAL  GEOLOGY. 


I .  Ice  of  Lakes  and  Rivers. 

The  ice  of  lakes  and  rivers  often  forms  about  stones  along 
their  shores,  and  sometimes  over  those  of  the  bottom  (then 
called  anchor-ice),  making  them  part  of  the  mass  ;  and  other 
stones  sometimes  fall  on  shore-ice  from  overhanging  bluffs. 
The  ice  serves  as  a  float  to  the  stones ;  and  in  times  of  high 
water,  or  floods,  it  may  carry  its  burden  high  up  the  shores, 
or  over  the  flooded  flats,  to  leave  them  there  as  it  melts. 
Large  accumulations  of  bowlders  are  sometimes  made,  by 
this  means,  on  shores  far  above  the  ordinary  level  of  the 
waters. 

2.  Glaciers. 

1.  Glaciers  are  ice-streams,  or  rivers  in  which  the  moving 
material  is  frozen  instead  of  liquid  water. 

Like  large  rivers,  they  ordinarily  have  their  sources  in  high 
mountains,  and  descend  along  the  valleys ;  but  (1)  the  moun- 
tains are  such  as  take  snow  from  the  clouds  instead  of  rain, 
because  of  their  elevation ;  and  (2)  they  must  be  high  and 
extensive  enough  to  take  annually  a  large  supply  of  snow 
from  the  clouds,  so  that  the  snow  may  accumulate  to  a  great 
depth ;  and  (3)  the  region  must  be  one  of  sufficient  precipi- 
tation. 

Like  lar^e  rivers,  many  tributary  streams  coming  from  the 
different  valleys  unite  to  make  the  great  stream. 

As  with  rivers,  their  movement  is  dependent  on  gravity,  or 
the  weight  of  the  material ;  but  the  average  rate  of  motion, 
instead  of  being  several  miles  an  hour,  is  generally  in  sum- 
mer but  10  to  18  inches  a  day,  or  ajnile  in  18  to  20  years. 
12  inches  a  day  corresponds  to  a  mile  in  14-|  years.  The 
rate  is  half  less  in  winter  than  in  summer. 

As  with  rivers,  the  central  portions  move  most  rapidly,  the 
sides  and  bottom  being  retarded  by  friction. 

The  snow  of  the  mountain-tops,  called  the  ntfve,  which  is 


GLACIERS.  117 

perhaps  hundreds  of  feet  deep,  becomes  compacted  and  con- 
verted into  ice  mainly  by  its  own  weight,  through  the  aid  of 
water  penetrating  it  derived  from  partial  melting ;  and  thus 
the  glacier  begins.  Through  the  occasional  melting  and  freez- 
ing, the  change  to  ice  is  made  more  complete.  As  the  glacier 
starts  on  its  course,  the  clouds  furnish  new  snows  to  keep  up 
the  supply  and  help  press  on  tliti  moving  mass. 

2.  Descent  below  the  snow-line,  —  The  height,  in  the  Alps, 
of  the  snow-line,  or  that  below  which  the  snow  annually  pre- 
cipitated melts  during  the  year,  is  8,000  feet  on  the  north  side 
of  the  Alps,  aad  8,800  feet  on  the  south  side ;  and  the  glacier 
descends  below  this  line  4,500  to  5,300  feet.     The  ice  resists 
the  melting  heat  of  summer  because  of  its  mass,  like  the  ice 
in  an  ice-house.     Though  starting  where  all  is  white  and 
barren,  it  passes  by  regions  of  Alpine  flowers,  and  often  con- 
tinues down  to  a  country  of  gardens  and  human  dwellings 
before  its  course  is  finally  cut  short  by  the  climate.     Thus, 
the  Bois  glacier,  an  upper  portion  of  which  is  called  the  Mer 
de  Glace,  rises  in  Mont  Blanc  and  other  neighboring  peaks, 
and  terminates,  like  two  other  glaciers,  in  the  vale  of  Cha- 
mouni.     In  a  similar  manner,  two  great  glaciers  descend  from 
the  Jungfrau  and  other  heights  of  the  Bernese  Alps  to  the 
plains  of  the  Grindelwald  Valley  just  south  of  Interlachen. 

Fig.  Ill  represents  one  of  the  ice-streams  of  the  Mount 
Eosa  region  in  the  Alps;  from  a  view  in  Professor  Agassiz's 
work  on  Glaciers.  It  shows  the  lofty  regions  of  perpetual 
snow  in  the  distance ;  the  bare  rocky  slopes  that  border  it, 
later  on  its  course;  and  the  many  crevasses  that  intersect  the 
surface  of  the  ice-stream. 

3.  Fractures   attending  the  movement.  —  Crevasses.  —  Every 
valley  has  its  ridgy  sides,  its  sharp  turns,  its  abrupt  narrow- 
ings  and  widenings,  its  irregular  bottom ;  and  the  stiff  ice, 
compelled  to  accommodate  itself  to  these  irregularities,  has, 
consequently,  profound  crevasses  made  usually  along  its  bor- 
ders, besides  multitudes  of  cracks  that  are  not  visible  at  the 
surface ;    also,  still   profounder  chasms  when  wrenched,  or 


118 


DYNAMICAL    GEOLOGY. 


stretched,  in  turning  some  point ;  longer  crevasses,  crossing 
even  its  whole  breadth,  when  the  ice  plunges  down  a  steep 
place  in  an  ice-cascade,  or  when,  on  escaping  from  a  narrow 
gorge,  it  moves  off  freely  again  with  increase  of  slope.  Again, 
it  may  lose  all  its  crevasses,  from  their  closing  up,  when  the 
rate  of  motion  is  lessened  by  diminished  slope  or  otherwise. 

Fig.  111. 


Glacier  of  Zermatt,  or  the  Corner  Glacier. 

4.  Glacier  torrent.  —  The  melting  of  the  glacier,  especially 
during  the  warm  season,  gives  origin  to  a  stream  of  water 
flowing  beneath  it,  which  becomes  gradually  a  torrent  of  con- 
siderable size,  and  finally  emerges  to  the  light  from  beneath 
the  bluff  of  ice  in  which  the  glacier  terminates.  Thence  it 
continues  on  its  rocky  course  down  the  valley. 


GLACIERS.  119 

5.  Method  of  movement.  —  The  capability  of  motion  in  a 
glacier  is  (Ij  dependent  partly  on  a  degree  of  plasticity  in  ice. 
Ice  may  be  made,  through  pressure,  to  copy  a  seal,  or  may  be 
drawn  out  into  cylinders ;   or,  if  a  slab  is  supported  only  at 
the  sides,  it  will  become  bent  downward,  through  gravity. 

(2)  It  is  also  due  in  part  to  the  facility  with  which  ice 
breaks.  The  ice  afterward  becomes  a  solid  mass  when  the 
broken  surfaces  are  brought  into  contact.  This  re-gelation 
was  first  noticed  by  Faraday.  It  is  easily  tried  by  breaking 
a  lump  of  ice  and  bringing  the  surfaces  again  into  contact : 
if  moist,  as  they  are  at  the  ordinary  temperature,  they  at  once 
become  firmly  united.  A  glacier  moves  on  and  accommo- 
dates itself  to  its  uneven  bed  by  bending  or  breaking ;  and, 
however  fractured,  it  may,  when  the  movement  slackens  and 
the  parts  are  pressed  together,  become  as  solid  as  before. 

Again  (3),  the  ice  is  everywhere  penetrated  by  water  during 
nearly  all  the  year,  and  this  diminishes  the  friction  within 
the  mass.  This  moisture  comes  from  above,  but  is  added  to 
below  because  of  the  heat  of  friction.  The  greater  amount  in 
summer  is  a  cause  of  the  more  rapid  movement  then. 

Again  (4),  a  glacier  may  here  and  there,  at  times,  slide 
along  its  bed,  yet  only  portions  at  a  time. 

6.  Transportation  by  Glaciers. — Moraines.  —  Glaciers  become 
laden  with  stones  and  earth  falling  from  the  heights  above, 
or  coming  down  in  crushing  avalanches  of  snow  and  stones. 

o  O 

The  stones  and  earth  make  a  band  along  either  border  of  a 
glacier,  and  such  a  band  is  called  a  moraine.  When  two 
glaciers  unite,  or  a  tributary  glacier  joins  another,  they  carry 
forward  their  bands  of -stones  with  them;  but  those  on  the 
uniting  sides  combine  to  make  one  moraine.  A  large  glacier, 
like  that  in  Fig.  Ill,  may  have  many  moraines,  —  or  one  more 
than  the  number  of  its  tributaries.  Some  of  the  masses  of 
rock  on  glaciers  are  of  immense  size.  One  is  mentioned 
containing  over  200,000  cubic  feet,  —  which  is  equivalent 
in  cubic  contents  to  a  building  100  feet  long,  50  wide,  and 
40  high. 


120  DYNAMICAL   GEOLOGY. 

The  ice  also  gathers  up  masses  of  rock  from  any  hillocks 
in  the  surface  beneath  it,  easily  detaching  and  bearing  off 
great  slabs  when  the  rocks  are  jointed  or  fractured. 

In  the  lower  part  of  a  glacier  the  several  moraines  lose 
their  distinctness  through  the  melting  of  the  ice;  for  this 
brings  to  one  level  what  was  distributed  through  a  consider- 
able part  of  its  former  thickness,  and  the  surface,  therefore, 
becomes  covered  with  earth  and  stones.  The  bluff'  of  ice 
which  forms  the  foot  of  a  glacier  is  often  a  dirty  mass,  show- 
ing little  of  its  real  icy  nature,  in  the  distant  view. 

The  final  melting  leaves  all  the  earth  and  stones  in  un- 
stratified  heaps  or  deposits,  to  be  further  transported,  eroded, 
and  arranged,  by  the  stream  that  flows  from  the  glacier. 

7,  Erosion  by  Glaciers,  —  A  glacier  laden  with  stones  will 
have  stones  in  its  lower  surface  and  sides,  as  well  as  in  its 
mass.  As  it  moves  down  the  valley,  it  consequently  abrades 
the  exposed  rocks  over  which  it  passes,  smoothing  and  pol- 
ishing some  surfaces,  covering  others  closely  with  parallel 
scratches,  and  often  ploughing  out  broad  and  deep  channels, 
besides  having  its  abrading  bowlders  scratched  or  pclished. 

Deep  ploughing  is  accomplished  only  (1)  when  the  rock 
beneath  is  soft  or  fragile,  or  (2)  when  it  is  jointed,  rifted,  or 
laminated.  In  the  latter  case  the  action  is  rending,  rather 
than  abrading,  and  by  this  means  the  larger  part  of  the 
direct  excavation  by  glaciers  has  been  done. 

The  rocky  ledges  over  which  the  ice  has  long  moved  are 
often  reduced  to  rounded  prominences  ;  they  then  look,  in  the 
distance,  like  groups  of  crouching  sheep,  and  hence  have  been 
called,  in  French,  roches  moutonnees.  They  are  exhibited  on 
a  grand  scale  in  some  of  the  valleys  of  the  high  ranges  along 
the  summit  of  the  Eocky  Mountains,  where  were  formerly 
extensive  glaciers;  and  Fig.  112  represents  one  of  the  scenes, 
in  the  region  of  the  "  Mountain  of  the  Holy  Cross  "  (the  re- 
moter summit  near  the  centre  of  the  view),  as  photographed 
by  the  photographer  of  the  Expedition  under  Dr.  Hayden. 
Further,  the  stones  in  the  ever-shifting  ice  wear  one  another, 


GLACIERS. 


121 


and  may  thereby  become  rounded  at  the  angles  ;  and  the  very 
fine  dust  thus  made  is  carried  down  by  the  waters  along  the 
crevasses  to  make  beds  of  clay  or  earth,  and  give  a  milky  hue 
to  the  streams  flowing  from  a  glacier  region. 


Fig.  112. 


View  on  Roche-Moutoimee  Creek,  Colorado. 


Glaciers  deepen  and  widen  the  valleys  in  which  they  move. 
But  in  this  work  they  are  aided  by  the  frosts,  avalanches,  and 
especially  by  the  torrents  beneath  the  glacier. 

8.  Glacier  regions.  —  The  best  known  of  Glacier  regions  are 
those  of  the  Alps,  in  one  of  which  Mont  Blanc  stands,  with 
its  summit  15,760  feet  above  the  sea.  There  are  glaciers 
also  in  the  Pyrenees,  the  mountains  of  Norway,  Spitzbergen, 
Greenland,  and  other  Arctic  regions,  in  the  Caucasus  and 
Himalaya,  in  the  Southern  Andes,  in  the  Coast  range  and 


122  DYNAMICAL   GEOLOGY. 

Kocky  Mountain  summits  of  British  America.  Greenland 
is  a  great  glacier- covered  land,  sending  many  large  streams 
through  the  fiords  of  the  border  region  to  the  polar  seas. 

3.   Icebergs. 

When  glaciers,  like  those  of  Greenland,  terminate  in  the 
sea,  the  icy  foot  becomes  broken  off  from  time  to  time,  through 
the  varying  movement  of  the  tides ;  and  these  fragments  of 
glaciers,  floated  away  by  the  sea,  are  icebergs.  The  geological 
effects  of  icebergs  have  been  stated  on  page  111.  Sea-shore  ice 
sometimes  carries  stones  and  gravel  far  out  to  sea. 


4.   Formation  of  Sedimentary  Strata. 

The  following  is  a  brief  recapitulation  of  the  explanations 
of  the  origin  of  deposits  given  in  the  preceding  pages.  Igne- 
ous and  other  crystalline  rocks  are  not  here  included. 

1.  Sources  of  material. — The  material  of  sedimentary  rocks, 
excluding  limestones,  has  come  mainly  from  the  degradation 
of  pre-existing  rocks.     But   another  part  (as  that  of  lime- 
stones, or  infusorial  earth)  has  been  taken  up  from  a  state  of 
solution  in  the  ocean  or  in  fresh  waters,  through  the  agency 
of  life ;  yet  the  waters  have  received  the  ingredients  from  the 
rocks,  either  when  the  ocean  first  began  to  exist,  or  subse- 
quently through  the  dissolving  action  of  streams  on  exposed 
rocks  (page  111). 

The  Archaean  rocks  were  the  original  source ;  and  in 
Eastern  North  America,  where  the  formations  of  the  Green 
Mountains  and  Appalachians  have  great  thickness,  Archaean 
ridges  existed  both  over  New  England  and  on  the  Atlantic 
borders. 

2.  Means  of  degradation. — The  principal  means  of  degrada- 
tion are  the  following:    1.  Erosion  by  moving  waters,  either 
those  of  the  sea  or  land  (pages  90,  107);  2.  Erosion  by  ice, 
either  that  of  glaciers,  icebergs,  or  ordinary  snow  and  ice 


FORMATION   OF   SEDIMENTARY  ROCKS.  123 

(page  120);  3.  Pressure  of  the  water  descending  into  fissures; 
4.  Forming  of  substances,  for  example  oxide  of  iron,  in  cracks, 
this  tending  to  open  and  deepen  the  cracks ;  5.  Growth  of 
rootlets,  roots,  and  trunks  of  trees,  in  crevices,  resulting  in 
opening  and  tearing  apart  rocks,  and  often  producing  exten- 
sive destruction  of  rocks,  especially  when  they  are  jointed ; 
6.  Freezing  of  water  in  fissures  (pa.ge  115);  7.  Chemical 
decomposition  of  one  or  more  of  the  ingredients  of  a  rock, 
in  the  course  of  which  process  the  rock  becomes  crumbled  or 
reduced  to  earth ;  8.  Kemoval  by  solution,  as  of  limestones  by 
carbonated  waters ;  9.  Undermining  of  rocks  by  any  method ; 
10.  Expansion  and  contraction  by  heat  (page  128.) 

3.  Formation  of  deposits  —  The  principal  methods  by  which 
deposits  have  been  formed  are  the  following :  — 

1.  By  the  waters  of  the  sea.  —  1.  Through  the  sweep  of  the 
ocean  over  the  continents  ivlicn  barely  or  partly  submerged, — 
making  (a)  sandy  or  pebbly  deposits  near  or  at  the  surface 
where  the  waves   strike,  or  at  very  shallow  depths   where 
swept  by  a  strong  current ;  (/;)  argillaceous  or  shaly  deposits 
near  or  at  the  surface,  where  sheltered  from  the  waves ;  and 
also,  at  considerable  depths,  out  of  material  washed  off  the 
land  by  the  waves  or  currents ;  but  not  malting  (c)  coarse 
sandy  or  pebbly  deposits  over  the  deep  bed  of  the  ocean,  as 
even  great  rivers  carry  only  silt  to  the  ocean  ;  and  not  mak- 
ing (//)  argillaceous  deposits  over  the  ocean's  bed  except  along 
the  borders  of  the  land,  unless  by  the  aid  of  a  river  like  the 
Amazon ;  in  which  case,  still,  the  detritus  is  mostly  thrown 
back  on  the  coast  by  the  waves  and  currents. 

2.  Through  the  waves  and  currents  of   the  ocean  acting 
on  the  borders  of  the  continent ;  the  results  are  the  same  as 
above,  except  that  the  beds  so  made  have  less  extent. 

3.  Through  living  species,  and  mainly  Mollusks,  Radiates, 
and  Khizopods,  affording  calcareous  material  for  strata ;  and 
Diatoms  and  some  Protozoans,  siliceous  material.    Most  rocks 
made  of  corals  and  the  shells  of  Mollusks  have  required  the 
help  of  the  waves,  at  least  to  fill  up  the  interstices. 


124  DYNAMICAL    GEOLOGY. 

2.  By  the  waters  of  lakes.  —  Lacustrine  deposits  are  essen- 
tially like  those  of  the  ocean  in  mode  of  origin,  unless  the 
lakes  are  small,  when  they  are  like  those  of  rivers. 

3.  By  the  running  waters  of  the  land.  —  1.  Filling  the  valleys 
with  alluvium  and  other  fluvial  deposits,  and  moving  the  earth 
from  the  hills  over  the  plains  (page  98).      2.  Carrying  detritus 
to  the  sea  or  to  lakes,  to  make,  in  conjunction  with  the  action 
of  the  sea,  or  lake-waters,  delta  and  other  sea-shore  accumu- 
lations (pages  99,  100). 

4.  By  frozen  waters.  —  A.  Acting  in  the  condition  of  gla- 
ciers, and  thus :    1.   Spreading  the   rocks  and  earth  of   the 
higher  lands  over  the  lower,  and,  in  the  process,  bearing  on- 
ward blocks  of  great  size,  as  well  as  finer  material  (pages  119, 
120).     2.  Distributing  rocks  and  earth  in  lines  or  moraines. 
—  B.  Acting  as  icebergs  ;  and,  in  this  condition,  transporting 
stones  and  earth  to  distant  parts  of  the  ocean,  as  from  the 
Arctic  regions  to  the  Newfoundland  Banks,  and  so  contribut- 
ing to  deep  or  shallow  water  or  shore  sedimentary  accumula- 
tions, distinguished  by  their  containing  huge  blocks  of  stone, 
besides  pebbles,  and  earth. 


V.— HEAT. 
1.  Sources  of  Heat. 

The  crust  of  the  earth  derives  heat  from  three  sources  : 
1.  The  sun,  an  external  source  ;  2.  The  earth's  heated  inte- 
rior ;  3.  Chemical  and  mechanical  action. 

1.  The  Sun.  —  This  agency  is  peculiar  in  being  regularly  in- 
termittent, through  the  alternations  in  the  seasons,  in  day 
and  night,  in  the  time  of  aphelion  and  perihelion,  and  in  the 
eccentricity  of  the  earth's  orbit.  The  amount  of  heat  im- 
parted to  the  earth  varies  also  with  the  density  of  the  atmos- 
phere, the  denser  atmosphere  absorbing  more  heat ;  and  it 
was  greater  in  early  time,  when  the  proportion  of  carbonic 
acid  and  of  moisture  was  greater  than  now.  The  following 


HEAT.  125 

are  some  of  the  causes  to  which  change  in  climate  has  been 
attributed  :  — 

1.  A  gradual  diminution  in  the  heat  of  the  sun  through 
the  geological  ages. 

2.  Variations  in  th.3  condition  of  the  sun's  exterior,  causing 
periodical  alterations  in  the  amount  of  heat  radiated,  and 
thus  producing  alternating  cold  and  warm  eras. 

3.  Variations  in  the  level  of  the  earth's  surface,  the  climate 
becoming  changed  when  extensive  regions  have  been  lifted  into 
mountains,  as  during  the  Tertiary  age,  or  when  great  areas  in 
high  latitudes  have  been  elevated  to  a  less  extent ;  and  espe- 
cially when  the  change  in  the  level  of  the  land  or  sea-bottom 
has  diverted  the  oceanic  currents  from  one  course  to  another. 
Elevating  the   sea-bottom   between   Europe   and   Greenland 
would  shut  out  the  warm  Gulf  Stream  from  the  Arctic  region 
and  increase  its  cold.     For,  according  to  Croll's  calculations, 
this  stream  contributes  to  the  North  Atlantic  Ocean  77,479,- 
650,000,000,000,000  foot-pounds  of  energy,  in  the  form  of 
heat,   per   day.     Such   a   change   might,  therefore,  make   a 
glacier-cold  climate  for  the  northern   hemisphere.      On  the 
contrary,  a  subsideaca  opaning  Behring  Straits  for  the  free 
passage  of  the  tropical  current  of  the  Pacific  would  amelio- 
rate the  arctic  climate. 

4.  Variations  in  the  eccentricity  of  the  earth's  orbit.     The 
earth,  through  all  such  variations,  derives  the  same  amount 
of  heat  annually  from  the  sun,  but   not  the  same  for  the 
winter  as  for  the  summer.     The  maxima  of  eccentricity  are 
unequal,  and  aro  passed  once  in  100,000  to  200,000   years. 
The  earth  is  at  present  near  a  minimum,  and  the  distance 
from  the  sun  h  about   93'9  millions   of  miles   in   aphelion 
(which  comes  now  in  summer),  and  nearly  90'9  millions  in 
perihelion  —  the  difference,  3  millions.     About  110,000  years 
since,  a  maximum  occurred,  with  the  aphelion  and  perihelion 
distances  96 '65  and  88*15  millions  of  miles  —  the  difference, 
8|  millions;  and  850,000  years  since,  an  extreme  maximum, 
with  these  distances,  99*3  and  85 '5  millions  —  the  difference 


126  DYNAMICAL  GEOLOGY. 

13 -8  millions  of  miles.  When  the  aphelion  comes  in  winter, 
the  cold  of  the  winters  is  increased,  the  amount  of  heat  re- 
ceived being  inversely  as  the  square  of  the  distance  (which 
ratio  gives  for  the  heat  in  winter,  during  the  extreme  maxi- 
mum referred  to,  about  fths  that  now  received  in  that  season); 
and,  also,  the  winter  half  of  the  year  between  the  equinoxes 
will  be,  at  the  extreme  maximum,  36  clays  longer  than  the 
summer  half  (now,  it  is  8  days  shorter) ;  at  the  same  time, 
the  summers  will  be  proportionally  hotter,  but,  in  the  same 
proportion,  shorter.  In  the  southern  hemisphere  the  reverse, 
in  each  respect,  is  true.  The  cold  of  a  Glacial  era  has  been 
thus  accounted  for,  and  also  the  warmth  of  warm  eras,  by 
Croll ;  but  others  reject  the  theory.  It  admits  of  two 
Glacial  eras  in  the  same  hemisphere  during  one  prolonged 
time  of  maximum,  since  the  aphelion  has  a  cycle  of  only 
21,000  years  ;  but  it  makes  the  southern  Glacial  era  to  come 
10,500  years  after  the  northern.  Further,  the  ice  of  a  Gla- 
cial era  tends  to  intensify  and  perpetuate  the  glacial  condi- 
tion, since  it  can  take  and  radiate,  even  in  the  sunshine,  no 
temperature  above  that  of  the  freezing-point. 

5.  A  change  in  the  earth's  axis  has  been  regarded  as  a 
source  of  variation  in  climate.  But  calculations  by  Mr.  G. 
H.  Darwin,  Haughton,  and  others,  have  shown  that  no  such 
change  can  have  taken  place  sufficient  for  any  marked  result. 

2.  Internal  Heat.  —  The  fact  of  a  high  heat  in  the  earth's 
interior  is  established  in  various  ways. 

1.  The  form  of  the  earth  is  a  spheroid,  and  a  spheroid  of 
just  the  shape  that  would  have  resulted  from  the  earth's  revo- 
lution on  its  axis,  provided  it  had  passed  through  a  state  of 
complete  fusion,  and  had  slowly  cooled  over  its  exterior. 
Hence  is  drawn  the  conclusion  that  it  has  passed  through 
such  a  state  of  fusion,  which  is  strengthened  by  the  other 
evidence  here  given.  Another  conclusion  also  follows :  namely, 
that  the  earth's  axis  had  the  same  position  (or,  at  least,  very 
nearly  the  same)  when  cooling  began  as  now.  There  is  no 
evidence  that  there  has  been  at  any  time  a  change. 


HEAT.  127 

2.  In  deep  borings  for  water  and  in  shafts  sunk  in  min- 
ing, it  has  been  found  that  the  temperature  of  the  earth's 
crust  increases,  on  an  average,  one  degree  of  Fahrenheit  for 
every  64  feet  of  descent.     The  rate  of  1°  F.  for  64  feet  of 
descent,  in  the  latitude  of  New  York,  would  give  heat  enough 
to  boil  water  at  a  depth  of  10,000  feet ;  and  at  a  depth  of 
about  35  miles  the  temperature  would  be  3,000°  F.,  or  that  of 
the  fusing-point  of  iron.     Since,  however,  the  fusing  tempera- 
ture of  any  substance  increases  with  the  pressure,  the  depth 
required   before  a  material   like  iron  would  be  found  in  a 
melted  state  would  be  much  greater  than  this.     Experiments 
on  the  temperature  in  artesian  borings  have  to  guard  against 
error  from  the  heat  caused  by  chemical  changes  in  the  rocks 
below,  such  as  decompositions  of  sulphides. 

3.  The  great  Pacific  Ocean  has  nearly  a  complete  girt  of 
volcanoes,  extinct  or  active ;  and  all  of  its  many  islands  that 
are  not  coral  are  wholly  volcanic  islands,  —  excepting  New 
Zealand  and  a  few  others  of  large  size  in  its  southwest  cor- 
ner.    Volcanoes  occur  along  many  parts  of  the  Andes  from 
Tierra  del  Fuego  to  the  Isthmus  of  Darien,  in  Central  America, 
in  Mexico,  California,  Oregon,  and  beyond ;  in  the  Aleutian 
Islands  on  the  north;   in  Kamtchatka,  Japan,  the   Philip- 
pines, New  Guinea,  New  Hebrides,  and  New  Zealand  on  the 
west;  and  on  Antarctic  lands  both  south  of  New  Zealand 
and  of  South  America.     The  volcanic  region  thus  bounded  is 
equal  to  a  whole  hemisphere ;  and,  besides,  there  are  vol- 
canoes in  many  parts  of  the  other  hemisphere.     Outlets  of 
lire  so  extensively  distributed  seem  to  indicate  that  there  is, 
or  must  formerly  have  been,  some   universal   seat   of   fire 
beneath. 

4.  The  flexures  which  the  earth's  crust  and  its  strata  have 
undergone  over  regions  of   continental  extent,  and  even  as 
late  as  the  Cenozoic,  indicate  that  there  have  been,  up  to  the 
middle  Cenozoic,  if  not  later,  as  great  regions  of  liquid  rock 
beneath  the  earth's  crust. 

3,  Chemical  and  Mechanical  action.  —  In  the  upturning  and 


128  DYNAMICAL  GEOLOGY. 

flexure  of  rocks  attending  mountain-making  there  have  been 
movements  on  a  grand  scale ;  and,  through  the  transforma- 
tion of  this  motion  into  heat,  the  rocks  have  received  in  some 
cases  a  high  temperature,  sufficient  to  promote,  through  the 
moisture  present,  the  consolidation  of  rocks,  and  even  their 
crystallization  or  metamorphism ;  and  also,  in  the  view  of 
Mallet,  their  fusion  on  a  scale  grand  enough  to  originate  vol- 
canoes. This  is  probably  one  chief  source  of  the  heat  through 
which  the  metamorphism  and  consolidation  of  rocks  have 
been  produced,  the  other  chief  source  being  the  internal 
heat. 

Heat  is  produced  by  condensation :  as  when  vapors  are 
condensed,  or  become  liquid  or  solid  ;  when  liquids  (as  water) 
become  solid ;  when  oxidation  or  other  like  change  takes 
place,  as  when  pyrite  oxidizes  (p.  82),  —  a  process  that  has  set 
fire  to  beds  of  coal. 


2.  Effects  of  Heat. 

The  following  are  the  effects  of  heat  here  considered :  — 

1.  Expansion  and  contraction. 

2.  Igneous  action  and  results. 
o.  Metamorpliism. 

4.  Formation  of  veins. 

5.  The  heat  of  the  globe  is  also  one  of  the  causes  of  earth- 
quakes, of  change  of  level  in  the  earth's  crust,  and  of  the 
elevation  of  mountains  :  these  subjects  are  considered  in  the 
following  chapter.      It  is  an  important   agent   also   in    all 
chemical  changes. 


0.     Expansion  and  Contraction. 

(1)  Heat  from  any  subterranean  source  penetrating  upward 
may  cause  wide  eliancjes  of  level  Lyell  has  calculated  that  a 
mass  of  sandstone  a  mile  thick,  raised  in  temperature  to  1,000° 


HEAT.  129 

F.,  would  have  its  upper  surface  elevated  50  feet.     Fractures 
and  displacements  would  be  likely  to  attend  such  movements. 

(2)  The  changing  heat  of  the  day,  which  in  some  countries 
amounts  to  80°  F.  or  more,  and  also  that  of  the  seasons,  is  a 
force  always  at  work.     The  expansion  and  contraction  may 
gradually  move  blocks  of  rock   from  their  places.     Tt  will 
move  the  heated  side  of  the  block  outward ;  and  if  this  outer 
part  so  moved  cannot,  because  of  any  wedging  or  the  friction 
at  the  edges,  return  with  the  succeeding  contraction,  the  mass 
will  move  to  it  or  have  its  edges  fractured.     The  Bunker 
Hill  obelisk  at  Charlestown  in  Massachusetts  has  been  proved 
to  swing  back  and  forth  with  the  passage  of  the  sun  over  it. 

(3)  The  alternating  action  of  expansion  and  contraction  peels 
off  the  grains  or  outer  surface  of  rocks,  and  is  a  prominent 
means  of  obliterating  glacier  markings. 

Slirinkagc-cracks.  —  (1)  In  the  cooling  of  liquid  rocks 
shrinkage-cracks  are  produced,  and  thence  come  the  colum- 
nar structure  of  trap,  basalt,  etc.  (page  48).  (2)  Similar 
columnar  forms  are  sometimes  produced  in  sandstone  after 
heating,  though  in  general  only  irregular  cracks  result. 
(3)  Heat  penetrates  rocks  over  wide  regions  wherever  meta- 
morphism  is  in  progress  ;  and  the  subsequent  cooling  and 
contraction  may  leave  multitudes  of  fractures,  in  long  lines 
or  in  reticulations,  the  subsequent  filling  of  which  may  make 
veins. 

Drying  is  another  source  of  shrinkage-cracks.  Tt  makes 
the  shallow  mud-cracks  (page  46),  the  deep  soil-cracks,  yards 
in  depth,  in  countries  of  fertile  prairies  that  have  a  long  hot 
and  dry  season,  and  may  produce  far  deeper  joint-like  cracks 
in  mud-made  rocks  (shales  and  argillaceous  sandstones)  as 
they  become  slowly  dried  from  subterranean  heat.  Further, 
the  drying  of  beds  produces  a  sinking  of  the  surface.  A  soft 
mud  may  contract  to  a  tenth  of  its  bulk.  All  mud-beds 
will  suffer  a  large  diminution  in  thickness  on  drying ; 
and  when  under  overlying  strata  the  pressure  may -prevent 
shrinkage-cracks  from  forming. 


130 


DYNAMICAL  GEOLOGY. 


2.   Igneous  Action  and  Results. 

A.  General  Nature  of  Volcanoes  and  their  products. 

Volcanoes  are  mountain-elevations  of  a  somewhat  conical 
form,  which  have  a  crater  at  centre,  and  eject,  from  time  to 
time,  streams  of  melted  rock.  If  the  fire-mountain  has  at 
present  no  active  fires  within,  and  is  emitting  no  vapors,  it  is 
said  to  be  extinct. 

Fig.  113. 


MOUNT  VESUVIUS:  from  a  sketch  by  the  author  in  June,  1834.  —n,  the  cone; 
6,  summit  cinder-cone  ;  c,  Somma,  part  of  former  outline  of  crater  ;  d,  Hermitage  (now 
Observatory) ;  e,  Portici  ;  /,  Herculaneum  ;  g,  Torre  del  Greco.  For  Map,  see  p.  398. 

The  cavity  or  pit  in  the  top  of  a  volcanic  mountain, 
called  the  crater,  where  the  lavas  may  often  be  seen  in 
fusion,  is  sometimes  thousands  of  feet  deep,  but  may  be 
quite  shallow ;  and  in  extinct  volcanoes  it  is  often  wholly 
wanting,  owing  to  its  having  been  left  filled  when  the  fires 
went  out. 

The  liquid  rock  issuing  from  a  crater,  and  the  same  after 
becoming  cold  and  solid,  is  called  lava. 


HEAT.  —  VOLCANOES.  131 

An  active  crater,  even  in  its  most  quiet  state,  emits  vapors. 
These  vapors  are  mostly  simple  steam,  or  aqueous  vapor ;  but 
in  addition  there  are  usually  sulphur  gases,  and  sometimes 
carbonic  acid  and  hydrochloric  acid. 

In  a  time  of  special  activity  fiery  jets  are  sometimes  thrown 
up  to  a  great  height,  which  are  made  of  red-hot  fragments,  — 
the  fragments  of  great  bubbles  of  lava  produced  by  the 
escaping  vapors.  The  fragments  cool  as  they  descend  about 
the  sides  of  the  crater,  and  are  then  called  cinders. 

When  a  shower  of  rain,  or  of  moisture  from  the  condensed 
steam,  accompanies  the  fall  of  the  cinders,  the  result  is  a 
mud-like  mass,  which  dries  and  becomes  a  brownish  or  yel- 
lowish-brown layer  or  stratum,  called  tufa.  Tufa  is  often 
much  like  a  soft  coarse  sandstone,  except  that  the  materials 
are  of  volcanic  origin. 

The  materials  produced  by  the  volcano  are,  then  —  1.  La- 
vas ;  2.  Cinders ;  3.  Tufas ;  4.  Vapors  or  Gases,  which  are 
mostly  vapor  of  water,  partly  sulphur  gases,  and  in  some 
cases  also  carbonic  acid,  hydrochloric  acid,  and  some  other 
materials. 

The  lavas  are  of  various  kinds.  They  are  more  or  less  cel- 
lular ;  sometimes  light  cellular,  like  the  scoria  of  a  furnace ; 
but  more  commonly  heavy  rocks,  with  some  scattered  ragged 
cellules  or  cavities  through  the  mass.  A  stream  of  lava  of 
this  more  solid  kind,  in  a  crater,  has  often  a  few  inches  of 
scoria  at  top,  —  as  a  running  stream  of  syrup  may  have  its 
scum  or  froth.  The  most  of  the  scoria  has  this  scum-like 
origin.  Pumice  is  a  very  light  grayish  scoria,  full  of  long  and 
slender  parallel  air-cells. 

The  black  and  brown  lavas  having  high  specific  gravity 
(above  2.8)  are  doleryte  and  related  kinds  containing  much 
pyroxene  or  hornblende ;  while  the  gray  or  light-colored 
kinds,  like  the  trachytes  (below  2.7  in  specific  gravity),  con- 
sist chiefly  of  a  feldspar  (see  p.  37). 

A  volcanic  mountain  is  made  out  of  the  ejected  materials ; 
either — (1)  out  of  lavas  alone  ;  or  (2)  of  cinders  alone ;  or  (3) 


132  DYNAMICAL   GEOLOGY. 

of  tufas  alone  ;  or  (4)  of  alternations  of  two  or  more  of  these 
ingredients.  As  the  centre  of  the  mountain  is  the  centre  of 
the  active  fires,  the  ejections  flow  off  or  fall  around  it,  and 
hence  the  form  of  a  volcanic  peak  necessarily  tends  to  become 
conical. 

The  average  angle  of  slope  of  a  lava-cone  is  from  3°  to  10°  ; 
of  a  tufa-cone,  15°  to  30°;  of  a  cinder-cone,  30°  to  42°;  of 
mixed  cones,  intermediate  inclinations  according  to  their  con- 
stitution. 

The  ordinary  slope  of  a  cinder  cone  is  shown  in  Fig.  113. 
Etna,  about  10,000  feet  high,  and  Mount  Loa  of  Hawaii, 
nearly  14,000  feet,  consisting  mainly  of  lava  streams,  have 
an  average  slope  of  less  than  10  degrees.  The  form  of  a  cone 
with  a  slope  of  7  degrees  —  which  is  the  average  for  the 
Hawaian  volcanoes  —  is  shown  in  Figs.  114,  115.  Fig.  114 
has  a  pointed  top,  like  Mount  Kea,  and  Fig.  115  a  rounded 
outline,  like  Mount  Loa,  whose  form  is  that  of  a  very  low 
dome. 

Fig.  114. 


B 

Mount  Kea. 

Fig.  115. 

Mount  Loa. 

The  highest  of  volcanic  mountains  on  the  globe  are  the 
Aconcagua  peak  in  Chili,  23,000  feet,  and  Sorata  and  Illi- 
raani,  in  Bolivia,  each  over  24,000  feet.  The  former  appears 
to  be  still  emitting  vapors,  showing  that  the  'fires  are  not 
wholly  extinct.  The  mountains  Shasta.  Hood,  St.  Helen's,  and 
others  in  California  and  Oregon,  are  isolated  volcanic  cones 


HEAT.  —VOLCANOES. 


133 


11,000  to  14,400  feet  high,  the  last  being  the  height  of  Mount 
Shasta.  The  average  slope  of  the  upper  half  of  Mount  Shasta 
is  about  27°.  The  slopes  of  most  of  the  lofty  volcanoes  of 
the  Andes  are  between  25°  and  34°. 


B.  Volcanic  Eruptions. 

The  process  of  eruption,  though  the  same  in  general  method 
in  all  volcanoes,  varies  much  in  its  phenomena.     The  funda- 


Fig.  116. 


Map  of  part  of  Hawaii. 

mental  principles  are  well  shown  at  the  great  craters  of  Ha- 
waii, the  southeasternmost  of  the  Hawaian  (or  Sandwich) 
Islands. 

1.  Hawaian  Volcanoes.  —  1.  General  description.  —  Hawaii  is 
made  up  mainly  of  three  volcanic  mountains,  —  two,  Mount 
Loa  and  Mount  Kea  (Figs.  114, 115,  p.  132),  nearly  14,000,feet 
high ;  and  one  (the  western),  Mount  Hualalai,  about  10,000 
feet.  Mount  Kea  is  alone  in  being  extinct. 


134  DYNAMICAL    GEOLOGY. 

Mount  Loa  has  a  great  crater  at  top,  and  another  inde- 
pendent one  4,000  feet  above  the  level  of  the  sea  (at  P,  Fig. 
117).  The  latter  is  the  famous  Kilauea,  called  also  Lua  Pele 
or  Pele's  pit,  Pele  being,  in  the  mythology  of  the  Hawaians, 
the  goddess  of  the  volcano. 

The  accompanying  map  of  the  southeastern  portion  of  Ha- 
waii, Fig.  116,  shows  the  positions  of  Mount  Loa  and  Mount 
Kea,  and  of  the  crater  of  Kilauea,  besides  other  craters  at  the 
summit  of  Mount  Loa,  and  at  P,  A,  B,  C,  K,  and  east  of  K. 

2.  Kilauea.  — The  crater  of  Kilauea  is  literally  a  pit.     It  is 
three  miles  in  greatest  length,  and  nearly  two  in  greatest 
breadth,  and  about  seven  and  a  half  miles  in  circuit.     It  is 
large  enough  to  contain  Boston  proper  to  South  Bridge,  three 
times  over,  or  to  accommodate  400  such  structures  as  St.  Pe- 
ter's at  Eome.    The  pit  has  nearly  vertical  sides  of  solid  rock 
(made  of  lavas  piled  up  in  successive  layers),  and  has  been 
1,000  feet  in  depth  after  several  of  its  eruptions,  and  400  to 
600  previous  to  its  eruptions.     The  bottom  is  a  great  area 
of  solid  lava,  with  one  or  more  lakes  or  pools  of  liquid  lava, 
or  crater-like  openings,  from  which  vapors  rise.     The  largest 
lake  was,  in  1840,  1,000  feet  in  diameter.     The  interior  may 
be  surveyed  from  the  brink  of  the  pit,  even  when  in  most 
violent  action,  as  calmly  and  safely  as  if  the  landscape  were 
one  of  houses  and  gardens. 

3.  Action  in  Kilauea.  —  The  ordinary  action,  as  well  exhib- 
ited in  several  great  eruptions,  is  simply  this.     The  lavas  in 
the  active  pools  are  in  a  state  of  ebullition,  jets  rising  and 
falling  as  in  a  pot  of  boiling  water, — with  this  difference,  that 
the  jets  are  30  to  100  feet  high.     Such  jets,  in  lava  as  well 
as  water,  arise  from  the  effort  of  vapors  to  escape ;  in  water 
the  vapor  is  steam  derived  from  the  water  itself ;  in  lavas  it 
is  chiefly  steam  from  waters  that  have  gained  access  to  the 
fires,  but  also  gases  derived  from  materials  in  the  lavas,  or 
from  depths  below. 

The  lavas  of  the  pools  or  lakes  overflow  at  times  and  spread 
in  streams  across  the  great  plain  that  forms  the  bottom  of  the 


HEAT.  —  VOLCANOES.  135 

crater.  In  times  of  great  activity  the  pools  and  lakes  are 
numerous,  the  ebullition  incessant,  the  jets  higher,  and  the 
overflowings  follow  one  another  in  quick  succession. 

4.  Cause  of  eruption.  —  By  these  overflows  the  pit  slowly 
fills.  In  the  intervals  between  1823  and  1832,  and  1832  and 
1840,  the  bottom  was  raised  400  feet  or  more  above  the  lowest 
level,  so  that  the  depth  was  reduced  from  1,000  to  600  feet 
or  less.  The  addition  of  400  feet  increased  400  feet  the 
height  of  the  central  column  of  liquid  lava  of  the  crater,  and 
caused  a  corresponding  increase  of  pressure  against  the  sides 
of  the  mountain.  The  amount  of  this  pressure  is  at  least 
two  and  a  half  times  as  great  as  that  which  an  equal  column 
of  water  would  produce.  The  mountain  should  be  strong  to 
bear  it.  The  lavas  at  such  times  may  be  in  a  state  of  violent 
activity,  and  a  large  addition  to  the  pressure  against  the  sides 
of  the  mountain  comes  from  the  force  of  the  imprisoned  vapors. 

The  consequence  of  this  increase  of  pressure,  both  from  the 
lavas  and  the  augmented  vapors,  may  be,  and  has  several 
times  been,  a  breaking  of  the  sides  of  the  mountain.  One  or 
more  fractures  result,  and  out  flows  the  lava  through  the 
openings.  Thus  simple  have  been  the  eruptions. 

In  the  eruption  of  1840  the  lavas  first  appeared  at  the  sur- 
face a  few  miles  below  Kilauea  (at  P,  Fig.  116),  and  then 
again  at  other  points  more  remote,  A,  B,  C,  m ;  finally  a  stream 
began  at  n,  a  point  20  miles  from  the  sea,  which  continued 
to  the  shores  at  Nanawale.  Here,  on  encountering  the  waters, 
the  great  flood  of  lava  was  shivered  into  fragments,  and  the 
whole  heavens  were  thick  with  an  illuminated  cloud  of  vapors 
and  cinders,  the  light  coming  from  the  fiery  stream  below. 
The  lavas  which  escaped  at  this  relatively  small  eruption 
amounted  to  at  least  15,400,000,000  cubic  feet. 

This  eruption  of  Kilauea  took  place,  it  will  be  observed, 
not  over  the  sides  of  the  crater,  but  through  breaks  in  the 
mountain's  sides  below;  and  the  pressure  of  the  column  of 
lava  within,  and  that  of  the  escaping  vapors,  appear  to  have 
caused  the  break. 


136 


DYNAMICAL  GEOLOGY. 


5.  Summit- crater  of  Mount  Loa.  —  Eruptions  have  also  taken 
place  from  the  summit-crater  of  the  same  mountain  (Mount 
Loa),  or  at  a  point  nearly  14,000  feet  high  above  the  sea ;  and 
in  each  case  there  has  been,  not  an  overflow  from  the  crater, 
but  an  outflow  through  breaks  in  the  sides  of  the  mountain. 

Fig.  117. 


ISLAND  OF  HAWAII.  —  L,  Mount  Loa;  K,  Mount  Kea  ;  H,  Mount  Hualalai  :  P, 
Kilauea  or  Lua-Pele  ;  1,  Eruption  of  1843  ;  2,  of  1852  ;  3,  of  1855  ;  4,  of  !Si9  ;  a,  Wahnea  ; 
6,  Kawaihae ;  c,  Wainaualii  ;  d,  Kaliua  ;  e,  Kealakekua  ;  /,  Kaulanamauna  ;  g,  Kailiki  ; 
h,  Waiohinu  ;  i,  Honuapo  ;  j,  Kapoho  ;  fc,  Nanawale ;  I,  Waipio  ;  ra,  first  appearance  of 
eruption  of  1868  ;  n,  Kahuku.  The  course  of  the  currents,  1,  2,  3,  and  5,  are  from  a  map 
by  T.  Coan,  and  4,  from  one  by  A.  F.  Judd. 

In  1852  there  was  first  a  small  issue  of  lavas  near  the  sum- 
mit, and  then  another  of  great  magnitude  about  10,000  feet 
above  the  sea-level.  At  this  second  outbreak  the  lava  was 
thrown  up  in  a  fountain,  or  mass  of  jets,  two  or  three  hundred 
feet  high ;  and  thus  it  continued  in  action  for  several  days. 
The  forms  of  the  fountain  of  liquid  fire  were  compared  by 


HEAT.  —  VOLCANOES.  137 

Kev.  Mr.  Coan  to  the  clustered  spires  of  a  Gothic  cathedral. 
Similar  lava  fountains  have  been  observed  also  at  other  erup- 
tions of  the  volcano. 

The  pressure  producing  the  jet  in  the  case  above  mentioned, 
so  far  as  it  was  hydrostatic,  was  that  of  the  column  of  lava 
between  the  point  of  outbreak  and  the  level  of  the  lavas  in 
the  summit-crater,  3,000  to  4,000  feet  above.  The  same 
pressure  in  connection  with  confined  vapors  must  have  caused 
the  breaking  of  the  mountain  in  which  the  eruption  began. 

Usually,  no  great  earthquakes  accompany  the  Hawaian  erup- 
tions, sometimes  not  even  slight  ones,  the  first  announcement 
being  merely  "  a  light  on  the  mountain."  Moreover,  when  the 
summit-crater  has  been  thus  active,  Kilauea,  though  10,000 
feet  lower  on  the  same  mountain  and  even  a  larger  pit-crater, 
commonly  shows  no  agitation,  no  signs  whatever  of  sympathy. 

The  black  bands  descending  from  the  summit-crater,  on 
the  map,  Fig.  117,  show  the  courses  of  four  great  outflows  of 
lava.  The  scale  of  the  map  is  38  miles  to  the  inch. 

6.  Conclusions. — These  cases  of  eruption  indicate  (I)  that 
the  lavas  go  on  gradually  increasing  the  pressure  in  the  in- 
terior by  their  accumulation,  while  augmented  activity  in  the 
production  of  vapors  increases  still  further  the  pressure ;  and 
that  finally  the  mountain,  when  it  can  no  longer  resist  the 
forces  within,  somewhere  breaks  and  lets  the  heavy  liquid 
out.  They  show  (2)  that  while  earthquakes  may  attend  vol- 
canic action,  they  are  no  necessary  part  of  it.  They  show  (3) 
that  lavas  may  be  so  very  liquid  that  no  cinders  are  formed 
during  a  great  eruption  ;  for  in  the  ebullition  of  the  lava  in 
the  boiling  lakes  of  Kilauea,  the  jets  (made  by  the  confined 
vapors)  are  usually  thrown  only  to  a  height  of  30  to  100  feet ; 
and  on  falling  back,  the  material  is  still  hot  and  does  not 
become  cooled  fragments ;  it  either  falls  back  into  the  pool  or 
lake,  or  becomes  plastered  to  its  sides.  The  liquidity  of  the 
lavas  is  shown  by  the  jetting  out  sometimes,  from  small  holes, 
of  drops  but  a  fourth  of  an  inch  thick,  which  fall  back  on  one 
another,  adhere,  and  so  make  a  model  of  a  little  fountain. 


138  DYNAMICAL  GEOLOGY. 

At  some  of  the  eruptions  of  Mount  Loa  the  lava  has  con- 
tinued down  the  mountain  to  a  distance  of  50  or  60  miles. 

2.  Vesuvius. — Vesuvius  is  an  example  of  another  type  of 
volcano.     The  lavas  are  so  dense  or  viscid  that  jets  cannot 
rise  freely  over  the  surface :  the  vapors  are  therefore  kept 
confined  until  they  form  a  bubble  of  great  dimensions ;  and 
when  such  a  bubble,  or  a  collection  of  them,  bursts,  the  frag- 
ments are  sometimes  thrown  thousands  of  feet  in  height.   The 
crater,  at  a  time  of  eruption,  is  a  scene  of  violent  activity, 
and  cannot  be  approached.      Destructive  earthquakes  often 
attend  the  eruptions. 

The  lavas  at  Vesuvius  may  flow  directly  from  the  top  of 
the  crater ;  but  they  generally  escape  partly,  if  not  entirely, 
through  fissures  in  the  sides  of  the  mountain. 

3.  Comparison  of   Mount   Loa  and  Vesuvius  as   to  causes  of 
eruption  and  nature  of  the  mountains.  —  Of  the  two  causes  of 
eruption,  —  hydrostatic  pressure   and   elastic   force   of  con- 
fined vapors,  —  the  latter  appears  to  be  the  most  effective  at 
Vesuvius,  while  the  former  may  be  at  Hawaii.     Mount  Loa, 
on  Hawaii,  is  an  example  of  the  great  free-flowing  volcanoes 
of  the  world,  and  the  mountain  is  almost  wholly  a  lava-cone. 
Vesuvius  is  an  example  of  a  smaller  vent  with  less  liquid 
lavas  ;  and  the  cone  is  made  up  of  both  solid  lavas  and  cin- 
ders.    The  activity  in  Mount  Loa  appears   to  be  kept   up 
mainly  by  the  fresh  waters  (rains)  which  fall  over  the  moun- 
tain and  descend  through  the  rocks  to  the  fires ;  while  Vesu- 
vius is  in  part,  at  least,  supplied  by  salt  waters  from  the 
Mediterranean,   as   is   proved   by    hydrochloric    acid  in  its 
vapors,  and    the    chlorides    among   its    saline   incrustations. 
The  waters  of  any  subterranean  streams  cannot  be  driven 
back  by  the  lavas,  owing  to  the  pressure  above,  and  hence 
they  must  enter  and  be  taken    up  by  the   lavas.     But   in 
all  volcanoes  there  must  be  a  gradual  supply  of  lavas  from 
below,  through  the  action  of  vapors  of  a  deep-seated  source, 
or  else  the  heat  would  sooner  give  out. 

4.  Trachytic  hills.  —  Feldspathic  lavas,  such  as  trachyte,  are 


HEAT.  —VOLCANOES.  139 

less  common  in  modern  volcanoes  than  the  dolerytic.  They 
have  in  some  cases  preceded  doleryte  in  the  history  of  a 
volcanic  cone.  They  are  less  fusible  than  the  latter,  because 
the  feldspar  orthoclase,  which  is  the  chief  constituent,  is  a 
mineral  of  rather  difficult  fusibility.  In  some  cases  these 
feldspathic  lavas  have  come  up  through  fissures  in  so  pasty  a 
state  that  they  have  swelled  up  into  steep  domes  and  cooled 
in  this  form.  Domes  of  this  kind  occur  in  Auvergne ;  also  in 
the  Black  Hills  (Newton  and  Jenny's  Eeport). 

5.  Lateral  cones  of  volcanoes.  —  In  eruptions  through  fissures 
the  lavas  may  continue  issuing  for  some  days  or  weeks  through 
the  more  open  or  widest  part  of  the  fissure,  and  consequently 
form  at  this  point  a  cone  of  cinders  or  lavas.     Thus  have 
originated  innumerable  cones  on  the  slopes  of  Etna  and  other 
volcanic  mountains. 

6.  Submarine  eruptions.  —  Eruptions  may  sometimes   take 
place  from  the  submarine  slopes  of  the  mountain  when  it  is 
situated  near  the  sea,  as  has  happened  with  Etna  and  Mount 
Loa ;  and  in  such  cases  accumulations  of  tufa,  or  of  solid 
lavas,  may  form  under  water  about  the  opened  vent.     Fishes 
and  other  marine  animals  are   usually  destroyed   in   great 
numbers  by  such  submarine  eruptions. 

7.  Subsidences  of  volcanic  regions.  —  Overwhelming  of  cities. 
—  Among  the  attendant  effects  of  volcanoes  are  the  sinking 
of  regions  in  their  vicinity  that  have  been  undermined  by 
the  outflow  of  the  lavas ;  the  tumbling  in  of  the  summit  of 
a  mountain ;  and  earthquakes,  or  vibrations  of  the  rocks  and 
also  of  the  air,  in  consequence  of  fractures.     Another  is  the 
burial,  not  only  of  fields  and  forests,  but  even  of  cities  and 
their  inhabitants,  by  the  outflowing  streams,  or  by  the  falling 
cinders  and  accumulating  tufas.     Pompsii  and  Herculaneum 
are  two  of  the  cities  that  have  been  buried  by  Vesuvius  ;  and 
every  few  years  we  hear  of  some  new  devastation  of  habita- 
tions or  farms  by  this  uneasy  volcano.     Pompeii  was  buried 
beneath   tufas  alone  ;   Herculaneum  lies  under   tufas,  lava- 
streams  of  several  later  eruptions,  and  aii  Italian  city. 


140  DYNAMICAL  GEOLOGY. 


C.  Subordinate  Volcanic  Phenomena. 

Solfataras.  —  In  the  vicinity  of  volcanoes,  and  sometimes 
in  regions  in  which  no  volcanoes  exist,  there  are  areas  where 
steam,  sulphur  vapors,  and  perhaps  carbonic  acid  and  other 
gases,  are  constantly  escaping.  Such  areas  are  called  sol- 
fataras  (from  the  Italian,  solfo,  sulphur,  and  terra,  earth). 
The  sulphur  gases  deposit  sulphur  in  crystals  or  incrusta- 
tions about  the  fumaroles  (as  the  steam-holes  are  called) ;  and 
alum  and  gypsum  often  form  from  the  action  of  sulphuric 
acid  (another  result  from  the  sulphur  gases)  on  the  rocks. 

Hot  springs.  — Geysers.  —  Fountains  or  springs  of  hot  waters 
are  common  in  places  of  this  kind,  and  are  often  so  abundant 
as  to  be  used  for  baths.  Such  springs  occur  also  in  many 
other  parts  of  the  world,  especially  in  regions  of  upturned  or 
of  eruptive  rocks.  In  some  cases  the  heat  is  produced  by 
chemical  changes  in  progress  beneath ;  but  often  the  source 
is  the  same  as  for  volcanic  heat. 

When  the  heated  waters  are  thrown  out  in  intermittent  jets 
they  are  called  geysers.  The  Yellowstone  Park  in  the  Rocky 
Mountains  (between  the  parallels  of  44°  and  45°  N.,  and  the 
meridians  of  110°  and  111°  W.)  is  the  most  remarkable  region 
of  geysers  in  the  world,  far  exceeding  that  of  Iceland.  One 
of  the  geysers  —  the  "  Beehive  "  —  is  represented  in  action  in 
Fig.  118.  The  action  of  geysers  is  owing  (1)  to  the  access  of 
subterranean  waters  to  hot  rocks,  producing  steam,  which 
seeks  exit  by  conduits  upward;  (2)  to  cooler  superficial 
waters  descending  those  conduits  to  where  the  steam  pre- 
vents farther  descent,  and  gradually  accumulating  until  the 
conduit  is  filled  to  the  top ;  (3)  to  the  heating  of  these  upper 
waters  by  the  steam  from  below  to  near  the  boiling  point ; 
when  (4)  the  lower  portion  of  these  upper  waters  becomes 
converted  into  steam,  and  the  jet  of  water  —  or  the  eruption 
—  ensues.  The  "Beehive"  jet  is  200  feet  high.  It  plays 
once  a  day;  others  play  every  hour= 


NON-VOLCANIC   IGNEOUS  EEUPTIONS.  141 

Heated  waters  act  on  the  rocks  with  which  they  are  in  con- 
tact and  decompose  them  ;  and  as  such  rocks  usually  contain 

Fig.  118. 


Beehive  Geyser  in  action. 

some  kind  of  feldspar,  they  become  slightly  alkaline  through 


142  DYNAMICAL    GEOLOGY. 

the  alkali  of  the  feldspar,  and  so  are  enabled  to  take  up 
silica  and  make  siliicom  solutions.  The  "soluble  glass,"  used 
as  a  cement,  is  a  sodium  silicate  like  that  of  the  geyser. 
The  silica  taken  into  solution  is  deposited  again  around  the 
geysers  in  many  beautiful  forms,  and  besides  makes  the  bowl 
or  crater  from  which  the  waters  are  thrown  out,  and  forms 
numerous  petrifactions. 

When  the  region  of  a  boiling  pool  consists  of  earth  or  mud, 
mud-cones  are  formed,  as  in  some  parts  of  the  Yellowstone 
Park,  and  also  at  Geyoer  Canon  (a  branch  from  Pluton 
Canon),  north  of  San  Francisco,  California. 

Besides  hot  springs  that  deposit  silica,  there  are  others  that 
deposit  calcium  carbonate,  making  thus  the  kind  of  porous 
limestone  called  travertine,  as  on  Gardiner's  River,  Yellow- 
stone Park. 

In  some  cases  the  action  of  the  heated  waters  on  the  rocks? 
exposed  to  them  gives  origin  to  deposits  of  quartz  crystals, 
agate,  opal,  and  different  silicates  and  other  minerals. 

D.  Igneous  Eruptions  not  Volcanic. 

It  has  been  stated  that  eruptions  of  volcanoes  generally 
take  place  through  fissures.  Fissure-eruptions  have  also  oc- 
curred in  regions  remote  from  volcanoes  ;  and  they  have  been 
the  source  of  ejections  over  the  western  slope  of  the  Rocky 
Mountains  vastly  greater  than  any  from  volcanic  centres. 
Such  fractures  of  the  crust  of  the  earth  must  have  descended 
to  some  seat  of  fires  or  liquid  rock.  Whatever  cause  was 
sufficient  to  break  through  to  the  fire-region  below  would 
have  sufficed  to  press  out  the  liquid  rock  from  beneath.  The 
narrow  mass  of  igneous  rock  which  fills  such  fissures  is  called 
a  dike  (page  43).  The  liquid  rock  has  sometimes  merely 
filled  the  fracture,  without  overflowing ;  but  in  other  cases  it 
has  spread  widely  over  the  surface,  making  strata  of  great 
extent  and  thickness.  The  outflow  of  liquid  rock  has  often 
been  followed  by  sedimentary  deposits  over  the  region,  and 


NON-VOLCANIC   IGNEOUS  ERUPTIONS.  143 

then  another  outflow  has  taken  place ;  thus  making  alterna- 
tions of  fire-made  and  water-made  strata. 

The  ordinary  rocks  of  dikes  are  described  on  page  38. 
The  igneous  rock  is  very  often  without  cellules  or  air-cavities  ; 
and,  if  any  are  present,  they  are  in  general  neatly  formed,  in- 
stead of  being  ragged  like  those  of  lavas.  Such  a  rock,  having 
the  cavities  filled  with  minerals  (as  quartz,  calcite,  zeolites, 
etc.),  is  called  an  amygdaloid.  The  rock  of  an  amygdaloid  is 
usually  hydrous  (and  chloritic)  throughout  (owing,  it  is  sup- 
posed, to  subterranean  waters  gaining  access  in  some  way 
while  the  eruption  was  in  progress) ;  and  the  cavities  were 
formed  in  the  outer  or  upper  part  where  the  diminished  pres- 
sure allowed  of  the  water's  passing  to  the  state  of  vapor. 

Dikes  are  common  on  all  the  continents,  especially  in  the 
regions  between  the  summits  of  the  border  mountains  and 
the  ocean  which  are  usually  between  300  and  800  miles  in 
breadth ;  as,  for  example,  between  the  Appalachians  and  the 
Atlantic,  and  between  the  Rocky  Mountains  and  the  Pacific. 

The  Pacific  slope  of  the  Rocky  Mountains  ^500  to  800 
miles  wide)  is  remarkable  for  its  lava  floods.  Some  of  them 
are  around  volcanoes,  or  volcanic  vents,  but  many  were  from 
fissure  eruptions  remote  from  any  central  source.  Along 
Snake  Elver  (the  southern  fork  of  the  Columbia),  in  Idaho, 
a  single  field  covers  24,000  square  miles,  and  is  275  miles  in 
length  from  east  to  west.  To  the  eastward  there  are  some 
volcanic  "  buttes,"  and  the  flow  appears  to  have  been  west- 
ward ;  but  it  is  evident  from  their  size  that  these  were  not 
the  source  of  the  widespread  lavas.  Of  the  many  successive 
outflows,  the  earliest  were  of  grayish  trachyte,  the  later,  of 
blackish  dolerytc  (C.  King).  As  usual  with  la, /as  coming 
from  great  depth  through  fissures  (where  pressure  prevents 
vapor-expansion),  no  scoria  occurs  over  the  surface. 

On  the  Upper  Columbia,  in  Oregon,  between  the  lofty  Mt. 
Hood,  with  its  fellows  of  the  Cascade  Range,  and  Lewiston, 
250  miles  to  the  eastward,  a  similar  lava-field  has  an  area  of 
30,000  square  miles,  or,  with  the  Mt.  Hood  region  included, 


144  DYNAMICAL  GEOLOGY. 

40,000.  For  long  distances  there  are  walls  bordering  the 
river  1,000  to  2,000  feet  high,  made  of  ranges  of  basaltic 
columns,  and  toward  Mt.  Hood,  the  thickness  is  3,500  feet. 
Again,  in  Northern  California,  south  of  the  combined  vol- 
canic area  of  Mt.  Shasta  and  Lassen's  Peak,  on  the  west 
slope  of  the  Sierra,  the  lavas  of  large  isolated  fissure-erup- 
tions were  so  copious  as  to  have  obliterated  the  deep  valleys 
of  an  old  system  of  drainage,  and  forced  the  streams  to  make 
new  channels.  The  erosion  then  begun  has  since  cut  out 
valleys  1,000  to  3,000  feet  deep,  partly  along  new  routes,  and 
far  down  into  the  subjacent  rocks,  leaving  the  remnants  of 
the  lava-field  as  caps  of  "Table  Mountains."  The  miners 
have  tunnelled  beneath  the  lava-cap  for  gold-bearing  gravels, 
and  found  rich  deposits  in  the  beds  of  the  old  streams. 
(J.  D.  Whitney.)  Nevada,  Southern  Utah,  Colorado,  New 
Mexico,  and  Arizona  have  other  wide  lava-fields. 

Still  more  wonderful  are  the  fissure  eruptions  of  the  Dec- 
can,  in  India,  where  a  railway  out  of  Bombay  runs  for  519 
miles  continuously  over  a  lava-field;  its  area  is  not  less  than 
200,000  square  miles. 

In  Eastern  North  America,  outflows  through  fissures  made 
the  Palisades  on  the  Hudson  ;  long  narrow  ranges  through 
the  Connecticut  valley,  including,  among  the  summits,  Mt. 
Tom  andMt.  Holyoke;  ridges  in  Nova  Scotia;  others  similar, 
at  intervals  from  New  Jersey  to  North  Carolina ;  and  others, 
in  the  vicinity  of  Lake  Superior.  The  rocks  of  the  Salisbury 
Craigs  near  Edinburgh,  and  of  the  Giants'  Causeway  and 
Fingal's  Cave,  are  other  examples. 

The  lava-streams  have  sometimes  alternated  with  sedimen- 
tary deposits,  made  largely  of  beds  of  tufa  and  called  "ash 
beds."  They  have  in  many  cases  intruded  between  pre-existing 
strata;  and  in  this  case  have  left  effects  of  the  heat  on  the 
overlying  as  well  as  the  underlying  bed,  that  is,  if  moisture  were 
present  to  help  the  heat.  Further,  the  intrusion  of  trachytic  lava 
has  at  times  lifted  the  overlying  strata  high  enough  to  make 
subterranean  dome-shaped  masses  1,000  to  4,000  feet  high 


NON-VOLCANIC  IGNEOUS  ERUPTIONS. 


145 


(named  laccoliths,  from  the  Greek  for  lake  and  stone) ;  as  in 
the  Henry  Mountains,  Southern  Utah,  where  denudation  has 
exposed  to  view  the  laccoliths.  (G.  K.  Gilbert.)  Ten  thou- 
sand feet  of  Tertiary  strata  are  described  as  having  been  thus 
lifted,  —  evidence  of  the  vastness  of  the  erupting  force. 

The  following  view  (from  a  sketch  by  the  author,  in  1840) 
represents  a  scene  of  columnar  basalt  in  Illawarra,  New  South 

Fig.  119. 


Basaltic  columns,  coast  of  Illawarra,  New  South  Wale.s. 

Wales,  another  region  of  fissure  eruptions.  The  verticality 
of  the  columns  is  proof  of  the  near  horizontality  of  the  flow 
of  basaltic  lava. 

3.  Metamorphism. 

1.  Metamorphism.  —  The  term  metamorphism  signifies  change 
or  alteration;  and,  in  Geology,  a  change,  in  the  earth's  rocks 
or  strata  demanding  some  heat,  but  less  than  for  fusion,  and 
resulting  in  crystallization,  or,  at  least,  firm   solidification. 
Such  changes  may  be  either  regional  or  local. 

2.  Regional    Metamorphism.  —  In    regional   metamorphism, 
the  regions  undergoing  change  have  often  been  thousands  of 
square  miles  in  area,  and  the  depth  to  which  the  alteration 
has  extended  has  sometimes  exceeded  30,000  feet.     The  rocks 
were  originally  uncrystalline  limestones,  shales,  sandstones, 

10        * 


146  DYNAMICAL   GEOLOGY. 

conglomerates.  They  are  changed  to  crystalline  limestone  or 
marble,  mica-schist,  gneiss,  and  the  like  (page  35).  They 
were  originally  in  horizontal  strata;  they  are  now  upturned 
or  folded,  and  are  often  intersected  by  veins. 

New  England  is  mostly  covered  by  metamorphic  rocks ; 
and  they  spread  over  the  eastern  border  of  New  York,  to 
New  York  Island.  They  are  the  rocks  of  the  Adirondacks 
and  much  of  Canada ;  of  the  Highlands  of  New  Jersey  and 
Putnam  County,  N.  Y. ;  of  the  Blue  Ridge  and  the  Black 
Mountains ;  of  a  large  area  south  of  Lake  Superior ;  of  high 
ranges  along  the  summit  of  the  Eocky  Mountains ;  and  of  the 
Sierra  Nevada  in  California.  They  occur  also  in  Scotland, 
Wales,  Cornwall,  Scandinavia,  and  various  other  countries. 

Proof  that  such  crystalline  rocks  are  metamorphic,  and  not 
igneous,  is  found  (1)  in  their  bedded  structure  answering 
usually  to  the  original  bedding  of  the  strata ;  and  (2)  in  the 
occurrence,  in  some  portions  of  a  metamorphic  stratum, 
where  the  change  is  least  complete,  of  unobliterated  fossils : 
as  in  part  of  the  marble  of  West  Rutland  and  other  places 
in  Vermont;  the  limestone  and  schists  near  Poughkeepsie 
and  elsewhere  in  Dutchess  County,  N.  Y. ;  in  the  Sierra 
Nevada ;  and  in  several  localities  in  Europe. 

3,  Effects.  —  The  effects  of  metamorphism  include :  — 

(1.)  Simple  compacting  and  solidification ;  as  in  making 
quartzyte  from  sandstone,  or  a  rock  looking  like  granite  from 
granitic  sandstone. 

.(2.)  A  change  of  color;  as  the  gray  and  black  of  common 
limestone  to  the  white  color,  or  the  clouded  shadings,  of  mar- 
ble ;  and  the  brown  and  yellowish-browp  of  some  sandstones 
colored  by  iron,  to  red,  making  red  sandstone  and  jasper-rock. 

(3.)  In  most  cases,  a  partial  or  complete  expulsion  of  water, 
but  not  in  all ;  for  serpentine,  a  metamorphic  rock,  is  one 
eighth  (or  13  per  cent)  water. 

(4.)  An  evolving  and  expulsion  of  mineral  oil  or  gas ;  as 
when  bituminous  coaljs  changed  to  anthracite  or  graphite. 

(5.)  An  obliteration  of  all  fossils ;  or  of  nearly  all  if  the 


METAMORPHISM.  147 

metamorphism  is  partial.     The  obliteration  is  usually  pre- 
ceded by  the  compression  and  distortion  of  the  fossils. 

(6.)  Often  a  change  in  crystallization  with  little  or  none  in 
chemical  constitution  ;  as  when  a  limestone  is  turned  to  white 
statuary  marble ;  and  a  sandstone  or  argillaceous  rock,  made 
from  the  granulation  of  granite,  gneiss,  and  related  rocks,  is 
changed  to  granite  or  gneiss  again. 

(7.)  In  many  cases,  a  change  of  constitution;  for  the  ingre- 
dients subjected  to  the  metamorphic  process  often  enter  into 
new  combinations  :  as  when  a  limestone,  with  its  impurities 
of  clay,  sand,  phosphates,  and  fluorides,  gives  rise,  under  the 
action  of  heat,  not  merely  to  white  granular  limestone,  but  to 
various  crystalline  minerals  disseminated  through  it,  such  as 
rnic<(,  fclds'par,  scapolite,  pyroxene,  apatite,  chondroditc,  etc. 

It  is  thus  seen  that  metamorphism  may  fill  a  rock  with 
crystals  of  various  minerals.  Even  the  gems  are  among  its 
results ;  for  topaz,  sapphire,  emerald,  and  diamond  have  been 
produced  through  metamorphic  action.  What  is  of  more 
value,  it  makes  out  of  rude  sandstones  and  limestones  crystal- 
line rocks,  as  granite  and  marble,  for  architectural  and  other 
uses.  Man's  imitations  of  nature  are  seen  in  his  little  red 
bricks. 

4.  Prosess.  —  Water  and  heat  are  two  agencies  essential  in 
metamorphism. 

Heat  is  important :  (1)  in  order  to  produce  that  weakening 
of  cohesion  in  and  among  the  particles  of  a  rock  which  is  the 
preparatory  step  toward  a  recrystallization  ;  and  (2)  in  order 
to  bring  about  the  chemical  changes  that  are  required,  nearly 
all  demanding  a  higher  than  the  ordinary  temperature,  though 
less  than  that  of  complete  fusion. 

Water  is  important  because :  (1)  dry  rocks  (as  illustrated  in 
a  fire-brick)  are  bad  conductors  of  heat ;  (2)  it  helps  greatly 
in  the  weakening  of  cohesion  ;  (3 )  it  takes  up  silica  and  alkali 
from  all  rocks  containing  feldspar  (p.  142)  if  heated  (and 
little  heat  is  necessary),  and  thus  becomes  a  siliceous  solution, 
which,  on  cooling,  may  deposit  the  silica  as  a  cement  among 


148  DYNAMICAL   GEOLOGY. 

the  grains  of  the  rock  and  so  promote  its  solidification  —  as  in 
altering  sandstone  to  quartzyte  —  and  may  also  deposit  quartz 
in  cavities  or  fissures ;  (4)  at  higher  temperature,  in  the  state 
of  steam  of  high  pressure,  it  decomposes  readily  most  of  the 
silicates  or  the  ordinary  minerals  of  rocks,  and  so  prepares  for 
the  formation  of  new  minerals  —  thus  making  soniet  lines  feld- 
spar, mica,  hornblende,  etc.  The  quartz  grains  of  a  sandstone 
have  often  had  the  grains  converted  into  minute  crystals  of 
quartz  by  the  deposition  of  silica  over  the  exterior. 

The  source  of  the  water  is  for  the  most  part  the  rocks  them- 
selves ;  for  beds  of  sandstone,  limestone,  etc.  contain,  before 
alteration,  on  an  average  at  least  2  per  cent  of  water  (inde- 
pendently of  any  in  spaces  between  the  beds),  which  means 
2  pints  of  water  to  100  pounds  of  the  rock ;  and  since  a  cubic 
inch  of  water  will  make  a  cubic  foot  of  steam  at  the  ordinary 
pressure,  this  agent  is  in  great  quantity,  and  is  well  distributed 
for  action. 

The  source  of  the  heat  is  (1)  partly  mechanical ;  for  meta- 
morphism  has  generally  taken  place  when  the  rocks  were 
undergoing  shovings,  foldings  and  faultings,  and  sometimes 
crushings  (see  page  128) ;  and  (2)  partly  also,  that  of  the 
earth's  interior  heat  conducted  upward  into  the  beds  (page 
127). 

These  are  some  of  the  various  ways  in  which  heated  and 
superheated  waters  have  aided  in  metamorphic  changes. 
Direct  experiments  have  shown  that  these  kinds  of  crys- 
tallizations do  result  from  the  action  of  heat. 

Quartz  crystals,  feldspars,  mica,  and  other  species  have 
been  artificially  made  by  the  subjection  of  the  ingredients  to 
highly  heated  moisture.  Siliceous  solutions  form  in  waters 
below  the  boiling  point ;  and  wherever  they  exist  they  may 
work  at  consolidation,  erosion,  and  the  making  of  layers  and 
veins  of  quartz.  Large  corals  in  Florida  have  been  hollowed 
out  by  this  means,  and  the  cavities  lined  with  quartz  crystals 
or  agate. 

The  fossils  of  a  limestone  have  been  silicified  and  flint 


METAMORPHISM.  149 

nodules  made  even  in  cold  waters.  The  ordinary  decompo- 
sition of  a  feldspar  or  mica,  of  hornblende  or  pyroxene,  — 
one  or  more  of  which  silicates  occur  as  constituents  of 
granite,  syenite,  trap,  porphyry,  trachyte,  and  of  beds  of  tufa 
when  first  deposited,  —  sets  free  silica  to  make  opal  or  quartz ; 
and  in  some  tufas  of  California  and  Colorado  the  clustered 
tree-trunks  of  a  former  forest,  as  well  as  scattered  logs  and 
stumps,  have  been  petrified  by  silica  from  such  a  source. 

Pressure  is  requisite  for  most  metamorphic  changes.  Lime- 
stone heated  without  pressure  loses  its  carbonic  acid  and 
becomes  quick-lime ;  but  if  under  pressure,  as  has  been  proved 
by  experiment,  the  carbonic  acid  is  not  driven  off.  The 
needed  pressure  may  be  that  of  an  ocean  above ;  it  may  be 
that  of  the  superincumbent  rocks,  and  a  few  hundred  feet 
only  would  suffice. 

The  similarity  of  an  argillaceous  sandstone  to  gneiss  or 
granite  is  often  much  greater  than  appears  to  the  eye.  When 
a  sandstone  has  been  made  out  of  a  gneiss,  it  may  have  the 
quartz  of  the  gneiss,  and  also  its  feldspar,  in  a  pulverized 
state,  along  with  its  mica  ;  so  that  the  change  produced  in  it 
by  metainorphism  might  be  mainly  a  change  in  state  of  crys- 
tallization. By  simply  heating  a  bar  of  steel,  and  cooling  it 
slowly  or  rapidly,  it  may  be  made  coarse  or  fine  steel,  the 
process  changing  the  grains  by  causing  the  molecules  of  the 
small  grains  to  combine,  to  make  large  ones  in  the  coarser 
kind,  and  the  reverse  for  the  finer.  There  is  something  analo- 
gous in  the  change,  above  described,  of  an  argillaceous  sand- 
stone to  gneiss  or  granite.  It  cannot  be  asserted,  however, 
that  the  feldspar  grains  in  the  sandstone  would  always  re- 
main feldspar;  they  may  contribute  to  the  making  of  mica 
and  a  mica-schist,  or  to  that  of  some  other  mineral  and 
rock. 

Often,  however,  the  material  derived  from  the  wear  of 
gneiss  and  granite  and  other  rocks  is  not  only  pulverized, 
but  also  more  or  less  decomposed.  The  feldspar,  for  example, 
may  have  lost  its  alkalies,  or  the  mica  its  oxide  of  iron  and 


150  DYNAMICAL  GEOLOGY. 

alkalies,  and  in  such  a  case  the  process  of  metamorphism 
could  not,  of  course,  restore  the  original  rock.  The  new 
rock  made  would  contain  no  feldspar  or  mica,  if  the  alkalies 
had  been  wholly  removed,  but  it  might  turn  out  an  argillite  or 
slate ;  or,  if  much  oxide  of  iron  is  present,  a  hornblende  rock, 
or  a  chlorite  rock,  or  some  other  kind  from  which  the  alka- 
lies, potash  and  soda,  are  absent. 

3.  Local  Metamorphism.  —  Local  metamorphism  has  often 
taken  place  in  the  walls  of  dikes  of  igneous  rocks,  or  in  the 
adjoining  parts  of  the  strata  over  or  between  which  they  have 
flowed,  in  consequence  of  the  heat  from  the  melted  and  cool- 
ing rock,  and  sometimes  after  cooling  has  ceased.  Near 
dikes  of  trap,  the  rock  is  sometimes  made  cellular  by  escap- 
ing steam,  and  filled  with  shrinkage-fissures  made  on  cooling 
or  drying ;  and  besides  these  effects,  various  minerals  have 
been  often  formed,  as  epidote,  chlorite,  hematite,  tourmaline, 
garnet,  out  of  the  ingredients  present  in  the  adjoining  strati- 
fied rock,  or  the  trap,  or  both,  —  which  are  true  examples 
of  metamorphic  results.  The  waters  of  mineral  springs,  es- 
pecially when  they  are  heated,  have  often  produced  meta- 
morphic effects  in  the  rocks,  and  many  mineral  species  have 
been  formed  by  these  means.  Such  cases  of  local  metamor- 
phism, as  well  as  the  facts  stated  on  page  148,  show  that  the 
mineral  changes  which  take  place  in  regional  metamorphism 
are  possible  and  natural  results  of  the  conditions  that  have 
existed  at  such  times. 


4.   Formation  of  Veins. 

L  Nature  and  origin  of  spaces  occupied  by  Veins.  —  Some  of 
the  forms  and  characters  of  veins  are  shown  and  explained 
on  page  42.  Veins  are  the  fillings  of  spaces  in  the  rocks  ; 
and  these  spaces  are  usually  (1)  the  cracks  or  fissures  made 
by  uplifting  or  disturbing  forces ;  (2)  by  the  expansion  or 
pressure  of  vapors  ;  (3)  by  shrinkage  from  cooling  or  drying ; 
they  may  be  (4)  the  openings  between  the  layers  or  lamina  of 


FORMATION  OF  VEINS.  .151 

a  rock  produced  in  the  flexing  of  the  beds,  like  those  between 
the  leaves  of  a  quire  of  paper  when  folded  over ;  or  (5)  open 
spaces  made  in  rocks  by  excavation,  as  caverns  are  made. 

The  uplifting  and  flexing  of  rocks  which  have  resulted  in 
fissures  and  openings  are  often  accompaniments  of  meta- 
morphic  change,  and  the  fissures  may  have  become  filled  before 
the  long  era  of  metaraorphism  had  passed.  The  heat  con- 
cerned in  such  a  case  may  be,  as  explained  above,  that  de- 
rived from  the  movements  in  the  strata  in  connection  with 
that  of  the  earth's  depths. 

2.  Materials  of  Veins.  —  Quartz  is  the  most  common,  be- 
cause siliceous  solutions  are  easily  made,  they  requiring  little 
heat.     Granitic  material,  requiring  higher  heat,  is  also  com- 
mon, but  especially  in  veins  intersecting  the  more  crystalline 
rocks ;    and  vein  granite  is  usually  much   coarser   in  crys- 
tallization than  ordinary  granite.    Other  stony  materials,  less 
common,  are    calcite.  bar  tie  (barium   sulphate),  and  fluorite 
(calcium  fluoride) ;  but  where  these  occur,  quartz  may  also 
be  present.     Along  with  the  earthy  minerals  may  occur  gold, 
or  the  various  ores  of  copper,  lead,  silver,  and  other  metals, 
besides  pyrite  (iron  sulphide)   which  is    almost  universally 
present  in  ore-bearing  veins  or  lodes.     The  earthy  minerals 
are  called  the  yangue  of  the  ore.     The  ores  are  usually  dis- 
tributed in  one  or  more  planes  parallel  with  the  walls  of  the 
vein  (Figs.  19,  20,  p.  42),  but  often  very  irregularly  ;  and  the 
veins  may  vary  greatly  in  size,  as  illustrated  in  Fig.  17,  and 
have  their  ores  only  in  their  broader  parts. 

3.  Origin  of  Dikes.  —  Fractures  that  reach  down  to  liquid 
rock  become  filled  by  it,  and  thus  dikes  are  formed  (page  43), 
which  are  not  true  veins,  though  sometimes  so  called. 

4.  Origin  of  Vein  Deposits.  —  The  following   are   common 
methods :  — 

1.  When  thefssures  or  openings  have  not  descended  to  liquid  rock, 
and  were  filed  from  either  side  or  below.  —  Vein  deposits  of  this 
kind  are  very  common.  They  include  nearly  all  those  con- 
sisting of  quartz  or  granite,  whether  containing  metallic 


152  DYNAMICAL    GEOLOGY. 

ores  or  not,  and  most  banded  mineral  veins  (page  42).  The 
fissures,  or  openings,  and  part  of  the  heat  are  a  result  of  pro- 
found disturbances  such  as  give  rise  also  to  metamorphisin. 
The  material  of  the  vein  is  brought  into  the  opening  from 
the  rock  adjoining,  either  that  directly  adjoining,  or  that  of 
depths  below.  The  fissured  rocks  being  heated,  as  above 
stated,  all  moisture  or  vapor  present  tends  to  decompose  the 
rock-material  near  the  fissure;  it  takes  alkalies  from  the 
feldspars,  and  so  becomes  siliceous,  and  few  minerals  will  with- 
stand its  action.  The  vapors  press  into  the  fissures  or  open- 
ings, carrying  the  mineral  material  they  can  dissolve,  and 
depositing  it ;  and  they  keep  up  supplying  material  until  the 
fissure  is  filled  or  the  supply  of  material  is  exhausted.  It  is 
natural  that  veins  in  gneiss  and  mica-schist  filled  in  this  way 
should  often  be  granitic  veins,  for  these  rocks  contain  the 
quartz,  feldspar,  and  mica  of  granite  ;  or,  that  they  should 
often  be  quartz  veins  simply,  which  they  are  likely  to  be  if 
the  temperature  is  not  high  enough  to  make  or  dissolve  feld- 
spar and  mica. 

Under  the  action,  whatever  metallic  ores,  or  constituents 
of  gems,  the  fissured  rock  contains,  are  carried  into  the  fissure 
with  the  other  mineral  material ;  and  additions  may  be  re- 
ceived largely  through  vapors  rising  from  its  deeper  parts. 

By  such  means  veins  have  been  supplied  with  their  gems 
and  ores.  The  quartz  veins  and  seams  in  the  slate  rocks  of 
a  gold  region  have  in  this  way  become  gold-bearing  veins,  the 
gold  and  quartz  having  been  brought  in  by  the  same  moisture, 
and  both  having  been  gathered  from  the  adjoining  or  under- 
lying rocks.  These  openings,  in  the  case  of  auriferous  quartz 
veins,  were  often  openings  between  layers  of  the  slate  made 
in  the  folding  or  upturning.  Quartz  veins  are  the  usual 
original  sources  of  gold ;  and  the  gold-bearing  gravels,  which 
afford  the  metal  by  simple  washing,  and  have  yielded  the 
larger  part  of  the  gold  in  use,  are  the  detritus  made  out  of  the 
gold-bearing  rocks.  The  same  gravels  often  afford  platinum, 
iridium,  and  diamonds. 


FORMATION   OF  VEINS.  153 

While  fissures  filled  by  this  lateral  inflow  of  material,  in 
connection  with  emanations  from  the  depths  below,  may  be 
uniform  in  material  across,  as  in  many  quartz  veins  or  seams, 
they  may  also  consist  of  bands  of  different  minerals,  like 
many  metallic  veins  (page  42).  In  the  formation  of  banded 
veins  the  process  has  brought  in  for  a  while  one  kind  of 
mineral,  as  quartz,  and  deposited  it  over  the  walls  of  the 
fissure;  then,  through  some  change,  some  other  mineral  or 
ore,  as  an  ore  of  lead,  or  one  of  zinc,  or  one  of  copper  ;  then 
quartz  again,  QT  fluorite,  or  calcite  ;  and  so  on  until  the  fissure 
was  filled. 

The  above  is  one  of  the  methods  by  which  the  earth's 
precious  metals  have  been  gathered  out  of  the  rocks,  in  which 
they  were  sparingly  disseminated,  into  generous  veins,  and 
thereby  placed  within  reach  of  the  miner. 

2.  Where  the  fissures  haw  descended  to  regions  of  liquid  rock  and 
were  filled  from  below.  —  (a)  Dikes  of  porphyry,  doleryte,  and 
related  rocks  are  sometimes  the  courses  of  veins  of  metallic 
ores.  The  veins  are  generally  situated  near  the  walls  of 
the  dike,  and  either  in  the  igneous  rock  or  in  the  rock 
adjoining. 

The  veins  may  have  been  made  (1)  when  the  dike  was 
made,  or  (2)  they  occupy  fissures  made  subsequently,  but 
during  the  same  epocli  of  disturbance,  or  (3)  they  have  been 
formed  later,  the  old  plane  of  fracture  being  a  plane  of  weak- 
ness liable  to  be  opened  anew.  The  metallic  materials  of  the 
vein  have  been  brought  up  as  solutions  or  vapors,  either  from 
the  depths  that  afforded  the  igneous  rock  itself,  or,  more 
probably,  from  the  walls  of  a  deep  part  of  the  fissure. 

The  veins  of  native  copper  at  Ke ween  aw  Point,  those  of 
the  same  metal  with  ores  of  copper  in  the  Eed  sandstone 
(Triassico-Jurassic)  of  the  Connecticut  Valley,  New  Jersey, 
and  Pennsylvania,  those  of  silver  ores  in  Nevada  and  other 
mines  along  the  Rocky  Mountains  and  Andes,  thus  originated, 
—  that  is,  in  connection  with  igneous  ejections ;  the  ores  not 
coming  up  as  a  constituent  part  of  the  igneous  rock,  but 


154  DYNAMICAL  GEOLOGY. 

mainly  through  the  aid  of  vapors,  and  often  those  of  subter- 
ranean waters. 

(b)  Frequently  in  regions  of  igneous  ejections  fissures  have 
been  made  that  have  received  not  igneous  rock,  but  only 
vapors  or  mineral  solutions  from  below,  and  thus  have  be- 
come metallic  veins.  Each  of  the  regions  just  mentioned 
contains  examples  of  such  veins. 

The  filling  may  continue  in  progress  long  after  the  igneous 
rock  is  cooled,  or  as  long  as  heated  vapors  continue  to  rise 
through  the  fissure.  Shrinkage-cracks  and  openings  made 
by  vapors  in  the  rock  adjoining  the  fissure  may  spread  the 
mineral  depositions  widely  on  either  side.  The  vent  may 
continue  as  a  source  of  heat  to  surface  waters,  making  hot 
mineral  springs  and  steaming  pools  or  basins,  about  or  from 
which  depositions  may  take  place  of  a  vein-like  character,  as 
is  going  on  now  in  Nevada  and  California. 

At  Leadville,  in  Colorado,  the  ores  of  silver  and  lead  occur 
in  veins  and  deposits  beneath  a  stream  or  bed  of  igneous 
rock  ;  and  they  probably  came  up  from  depths  below  through 
the  fissures  which  were  opened  at  the  time  of  eruption,  but 
which  may  have  long  given  passage  to  hot  vapors.  The 
original  material  in  the  depths  below  may  have  been  chiefly  a 
silver-bearing  galenite  (lead  sulphide) ;  but  through  the  heat 
and  vapors  from  those  depths,  and  ingredients  met  with  above, 
they  are  now  different  ores  of  silver,  along  with  silver-bearing 
galenite,  mixed  with  lead  carbonate,  lead  sulphate,  iron  oxide, 
and  other  minerals,  and  much  disguised  by  the  mixture.  They 
occur  mostly  in  connection  with  a  limestone  that  was  greatly 
eroded  in  the  process. 

3.  Fissures  or  cavities  filed  by  infiltration  or  deposition  from 
above.  —  Wide  cracks  opening  to  the  surface  have  sometimes 
been  filled  with  sand  or  earth,  producing  a  kind  of  vein  or 
dike.  Small  cracks  through  rocks,  shrinkage-cracks,  and 
others  have  often  been  filled  with  calcite  by  infiltration  from 
above,  and  sometimes  by  other  minerals  held  in  solution  by 
infiltrating  waters. 


FORMATION  OF  VEINS.  155 

Depositions  of  galenite  or  lead  ore  (with  sometimes  nickel 
and  zinc  ores)  have  taken  place  in  cavities  or  caverns  in  lime- 
stones, as  in  Wisconsin,  Illinois,  and  Missouri,  and  Cumber- 
land and  Derbyshire,  England.  The  ore  is  often  supposed  to 
be  in  veins,  when,  actually  in  local  deposits  that  were  made  by 
supplies  from  above.  Yet  they  often  have  great  extent,  and 
are  a  valuable  source  of  ore,  as  in  the  American  localities  men- 
tioned (as  first  deduced  by  J.  D.  Whitney),  and  probably  in 
many  others.  The  condition  of  the  ore-beds  shows  that  when 
the  deposition  was  in  progress,  the  limestone  underwent  much 
erosion  from  acid  solutions  concerned  in  or  resulting  from  the 
changes. 

Many  cases  of  extensive  bodies  of  ore  in  cavities  in  lime- 
stone appear  not  to  be  of  the  above-mentioned  kind,  but  to  be 
properly  vein  deposits.  They  may  in  some  cases  have  origi- 
nated in  fissures  which  produced  ore-deposits  only  where  they 
intersected  limestones,  because  only  limestones  were  easily 
rendered  cavernous  by  the  eroding  vapors  so  as  to  afford 
spaces  for  the  ores. 

5.  So-called  veins  that  are  not  true  veins.  —  In  the  course  of 
the  earth's  rock-making,  metallic  ores  have  often  been  de- 
posited along  with  the  detritus  when  a  sedimentary  bed  was  in 
progress  of  formation  ;  they  have  been  brought  into  marshes, 
or  spread  over  confined  sea-margins  and  mud-flats,  by  run- 
ning waters  which  took  up  the  metal  (in  some  soluble  state 
of  combination)  from  the  decomposing  rocks  of  the  region 
around.  Deposits  of  iron  ores  are  thus  made  at  the  present 
time  (page  85),  and  those  also  of  zinc,  cobalt,  nickel,  and 
copper  were  so  made  in  early  geological  ages.  When  strata 
containing  such  metalliferous  layers  have  undergone  uplifts 
and  crystallization,  the  nearly  vertical  beds  look  like  veins. 
The  great  deposits  in  the  Archaean  terranes  of  hematite  an  3 
magnetite  are  beds,  not  veins  or  dikes. 


156  DYNAMICAL  GEOLOGY. 

i 

V.  — MOVEMENTS  IN  THE  EARTH'S  CRUST: 
THEIR  CAUSES  AND  CONSEQUENCES. 

As  a  preparation  for  the  study  of  the  following  pages,  it  is 
important  that  the  subject  of  flexures,  fractures,  and  displace- 
ments, explained  on  pages  52-56,  should  be  well  understood, 
and  also  that  the  facts,  on  pages  217  and  276-281,  connected 
with  the  making  of  the  Green  Mountains  and  Appalachians 
should  have  been  previously  perused. 

1.  Explanations  already  given.  —  In  the  preceding  chapters 
the  origin  of  many  geological  phenomena,  and  of  some  of  the 
earth's  features,  have  been  briefly  explained. 

A.  Changes  of  level  have  been  described  as  caused  (1)  by 
change  of  temperature,  this  cause  producing  the  expansion 
and  contraction  of  rocks  (p.  128);  (2)  by  undermining  due  to 
subterranean  water  (p.  102) ;   (3)  by  undermining  due  to  vol- 
canic outflows  (p.  139). 

B.  Mountain  forms  have  been  described  as  often  a  result  of 
the  sculpturing  of  elevated  plateaus  of  nearly  horizontal  rock 
by  streams,  as  exemplified  among  some  of  the  most  majestic 
mountains  of  the  globe  (p.  95). 

C.  Folding  of  beds  has  been  shown  to  have  been  caused 
when  they  are  clayey,  soft,  and  wet,  by  a  lateral  movement 
produced  through  the   pressure  of  superincumbent  material 
(p.  106). 

D.  Fractures  and  faultings  of  strata  have  been  attributed  (1) 
to  undermining  by  different  methods  (pp.   102,  139);  (2)  to 
contraction  or  expansion  ;    (3)  to  shrinkage  on  drying,  pro- 
ducing deep  or  shallow  fractures  (p.  129) ;  (4)  to  the  expan- 
sive force  of  vapors  (p.  135) ;  (5)  to  the  hydrostatic  pressure 
of  a  column  of  lava  (p.  135)  ;  and  to  other  causes. 

E.  Lamination  parallel  to  the  bedding,  as  in  the  shaly  struc- 
ture, has  been  explained  as  a  possible  result  of  the  pressure 
to  which  wet  argillaceous  beds  have  been  subjected  through 
the  weight  of  overlying  strata. 


MOVEMENTS    IN   THE   EARTH'S  CRUST  157 

F.  Metamorphism  has  been  described  as  produced  on  a  small 
scale,  (1)  in  the  vicinity  of  dikes  of  igneous  rock,  through  the 
heat  of  the  rock  when  it  was  cooling  from  fusion,  if  vapors 
or  moisture  were  present  to  aid ;  and  (2)  also  in  the  neigh- 
borhood of  hot  springs  (p.  150). 

G.  Earthquakes  have  been  stated  to  result  from  fractures  of 
rocks  in  subterranean  regions,  consequent  (1)  on  undermining 
(p.  102) ;  or  (2)  on  movements  and  fractures  attending  volcanic 
action  (p.  139). 

But  none  of  the  causes  that  have  been  considered  explain 
the  great  changes  of  level  involving  large  parts  of  continents 
or  of  oceanic  areas ;  or  the  phenomena  attending  the  making 
and  uplifting  of  mountains;  or  the  widespread  or  regional 
metamorphism  that  has  turned  simultaneously  sedimentary 
beds  over  thousands  of  square  miles  into  crystalline  rocks ;  or 
the  earthquakes  that  have  shaken  a  hemisphere. 

2.  Relation  in  size  between  the  earth  and  its  mountains. — 
On  a  globe  twelve  feet  in  diameter,  the  height  of  the  earth's1 
loftiest  mountains  would  be  represented  by  an  elevation  of 
about  one  twelfth  of  an  inch ;  the  whole  difference  of  level 
between  the  deepest  part  of  the  oceanic  basin  and  the  highest 
point  of  the  land,  by  twice  this  amount ;  and  the  mean  depth 
of  the  ocean,  by  a  depression  of  one  twentieth  of  an  inch.     The 
deformation  of  the  sphere  produced  in  the  making  of  the  con- 
tinents and  mountains  was,  therefore,  very  small. 

3.  Facts  as  to  changes  in  level  that  are  explained  by  a  change 
in  water-level.  —  The  subject  of  the  origin  of  changes  of  level 
is  complicated  by  the  fact  that  the  base  from  which  such 
changes  are  measured  is  the  water-plane  of  the  ocean,  and 
this  is  far  from  constant,  especially  in  the  vicinity  of  the 
continents. 

(1.)  The  deepening  of  any  part  of  the  oceanic  basin  would 
produce  apparent  elevation  of  the  land ;  and  the  thousand 
feet  of  mean  elevation  of  the  land  above  the  ocean  has  been 
attributed  to  this  cause. 

(2.)  The  lifting  of  mountains  on  a  continent,  or  the  piling 


158  DYNAMICAL  GEOLOGY. 

of  ice  to  mountain  heights  (as  in  a  Glacial  era),  makes  the 
pendulum  move  some  seconds  of  arc  toward  the  high  region, 
and  alters  correspondingly  the  level  of  the  adjoining  ocean, 
and  thus  draws  the  waters  over  the  land,  diminishing  the 
actual  height  of  the  mountains  above  the  sea ;  even  a  thou- 
sand feet  of  height  in  the  land  causing  a  displacement  in  the 
pendulum  and  level,  as  has  been  found  in  different  regions, 
of  five  or  six  seconds. 

(3.)  The  accumulation  of  ice  of  great  thickness  about  either 
pole  would  change  the  level  of  the  ocean  from  the  pole  to  the 
equator,  and  in  proportion,  approximately,  to  the  sine  of  the 
latitude ;  it  would  cause  a  like  displacement  in  the  pen- 
dulum and  level,  and  hence  diminish  the  slope  southward  of 
the  land  of  a  continent,  besides  submerging  to  some  extent 
the  coast  regions.  The  same  result  would  follow  from  an 
increase  in  the  solid  material  of  the  arctic  area  through  detri- 
tus from  northward-flowing  rivers.  But  there  would  be  no 
effect  in  either  case  provided  the  crust  beneath  subsided  to 
an  equivalent  amount. 

(4.)  A  gradual  retardation  of  the  earth's  rotation  (such  as 
tidal  friction  tends  to  occasion)  would  diminish  centrifugal 
iction,  and  hence  should  lead  to  a  diminution  in  the  depth  of 
equatorial  waters  (involving  an  emergence  of  tropical  land), 
and  to  an  increase  in  that  of  the  polar,  provided  a  sinking  of 
the  tropical  crust  does  not  take  place  as  a  consequence  of  the 
change.  The  fact  that  the  great  mountain  chain  of  Western 
America  is  lowest  in  a  portion  of  its  tropical  part  is  the  oppo- 
site of  that  which  the  retardation  alone  should  produce. 

4.  Facts  as  to  changes  in  level  that  are  not  explained  by 
changes  in  water-level  or  the  earth's  attraction.  —  Some  of  the 
above  causes  have  produced  effects  which  the  geologist  has  to 
study  out.  But  the  grander  changes  of  level  are  not  thus 
explained ;  and  if  not  the  grander,  then  not  the  larger  part  of 
the  smaller.  The  raising  of  mountain  ranges,  with  the  accom- 
panying upturning  or  flexing,  faulting  and  metamorphism  of 
slrata,  have  some  other  explanation.  The  lifting  of  a  marine 


MOVEMENTS  IN  THE  EARTH'S  CRUST.  159 

formation  —  as  the  Cretaceous,  with  the  crust  it  rests  on  — 
ten  thousand  feet  higher  in  the  Eocky  Mountains  than  on 
the  Atlantic  border,  is  an  example  of  a  large  class  of  facts  to 
be  explained  by  some  different  method ;  and  so  is  the  lifting 
of  the  same  beds  along  the  whole  length  of  the  mountains 
from  Central  America  to  the  Arctic,  but  with  maximum  effect 
within  the  area  of  the  United  States.  The  subsidence  of  great 
areas,  in  some  cases  10,000  to  40,000  feet,  —  the  maximum 
exceeding  the  maximum  depth  of  the  ocean,  —  during  the 
accumulation  of  beds  for  mountain-making,  is  another  effect 
of  some  different  cause ;  and  so  are  pr'obably  very  many  of 
the  gentle  oscillations  of  level  which  have  attended  the  depo- 
sition of  the  successive  strata  of  a  formation,  as  those  of  the 
Carboniferous  age. 

5.  Bearing  of  facts  as  to  the  direction  of  action  of  the  moun- 
tain-making force.  —  The  characteristics  of  the  force  at  work 
in  mountain-making  are  to  be  largely  learned  from  the  results 
produced.  The  following  are  some  of  these  results  :  — 

(1)  It  has  placed  the  mountains  mostly  along  the  borders 
of  the  continents ;  (2)  it  has  made  the  highest  mountains  on 
the  borders  of  the  largest  oceans ;  (3)  it  has  pressed  up  strata 
many  thousands  of  feet  in  thickness  into  great  folds,  some 
exceeding  10,000  feet  in  height,  and  forced  fold  against  fold, 
in  succession,  over  breadths  of  one  or  more  hundred  miles, 
and  along  belts  a  thousand  and  more  miles  in  length ;  (4)  it 
has  made  more  numerous  and  much  steeper  flexures,  and 
more  metamorphism  and  igneous  eruptions,  on  one  side  of  a 
mountain  range  than  on  the  other,  so  that  a  mountain  range 
is  a  one-sided  structure ;  (5)  it  has  often  made  the  larger  part 
of  the  flexures  correspondingly  one-sided ;  that  is,  with  one 
slope  steeper  than  the  other. 

The  points  here  enumerated  are  well  illustrated  on  the 
pages  already  referred  to.  Unequal-sided  flexures  are  repre- 
sented in  the  sections  from  Pennsylvania  and  Virginia  on 
page  279 ;  and  in  the  figures  (by  Prof.  Lesley)  on  page  97, 
which,  although  ideal,  present  actual  facts  from  the  up- 


160  DYNAMICAL  GEOLOGY. 

turned  rocks  of  Pennsylvania.  The  ideal  section  on  page  55 
(Fig.  47)  exemplifies  the  common  fact  as  to  crowded,  steep 
reversed  folds  on  one  or  the  other  side  of  a  mountain  area  of 
steeply  flexed  rocks :  as  is  well  illustrated  in  the  Appalachian 
chain  from  Alabama  to  New  England  and  beyond. 

The  following  figure  represents  a  vertical  section  of  the 
anthracite  region  between  Neshquehoning  Valley  (on  the 
west,  left  in  section,)  and  Mauch  Chunk.  (From  the  Keport 

Fig.  120. 


Section  of  the  Panther  Creek  Anthracite  basin  at  Nesquehoning  tunnel  (T). 

of  C.  A.  Ashburner  of  the  Geological  Survey  of  Pennsylvania 
under  Prof.  Lesley.)  The  length  is  about  1,200  yards  (the 
scale  of  the  figure  being  1,000  feet  to  the  inch).  The  flex- 
ures to  the  west  have  their  summits  pushed  westward  40° 
beyond  the  vertical.  The  folded  rocks  consist  of  beds  of 
anthracite  and  intervening  strata  of  shale  and  sandstone ; 
and  the  anthracite  beds  include  the  great  "  Mammoth  bed  " 
(lettered  at  its  outcrop  E,  E1,  E2)  which  is  13  to  27  feet  thick, 
and  the  bed  F  (outcropping  at  F1,  F2,  F3,  F4,  F5)  11  to  20  feet 
thick,  besides  one  of  8  to  9  feet.  The  "  Mammoth  bed,"  is 
doubled  on  itself  at  E1. 

The  facts  thus  far  published  sustain  the  conclusion  that 
the  mountain  ranges  of  the  Appalachian  chain,  and  the 
most  of  the  flexures  of  the  included  strata,  are  inequilateral. 
The  Eocky  mountain  region  exhibits  this  feature  in  .having 


MOVEMENTS  OF  THE  EARTH'S  CRUST.     161 

several  great,  nearly  parallel,  mountain  ranges  between  its 
summit  and  the  Pacific — among  them,  the  Wahsatch  Moun- 
tains, the  Humboldt  ranges,  the  Sierra  Nevada  and  Cascade 
Kange,  and  the  Coast  Kange  —  and  almost  nothing  to  corres- 
pond on  the  eastern ;  in  having  its  areas  of  igneous  rocks 
confined  almost  wholly  to  the  western  slopes,  with  its  great- 
est line  of  volcanoes  not  far  from  the  ocean's  border ;  and  in 
having  metamorphic  rocks  widely  distributed  on  the  western 
side,  and  sparingly  on  the  eastern. 

Thus  it  is  proved  that  the  force  has  in  general  acted 
laterally,  that  is,  from  one  side,  as  the  pushing  side,  and 
that  it  was,  therefore,  lateral  pressure^  however  it  may  have 
been  occasioned.  It  is  to  be  noted  that  it  has  produced  its 
greatest  effects  along  the  borders  of  the  continents  over  an 
area  one  to  eight  hundred  miles  wide.  It  has  made  long 
ranges,  by  simultaneous  action,  along  the  course  of  the  pro- 
gressing uplift,  and  has  acted  from  nearly  the  same  direction 
in  all  the  uplif tings  of  any  region  from  Archaean  time  to  the 
present. 

6.  Bearing  of  known  facts  on  the  question  as  to  the  earth's 
interior  condition.  —  From  the  great  subsidences,  —  like  that 
of  30,000  feet  or  more,  which  was  a  prelude  to  the  making  of 
the  Appalachians,  —  it  may  be  inferred  that  plastic  rock  exists 
beneath,  to  be  pushed  aside  so  as  to  render  subsidence  pos- 
sible. The  great  elevations  have  been  explained  only  upon  the 
assumption  of  a  flexible  crust  overlying  something  plastic. 

The  earth  is  believed  to  have  slowly  cooled  from  a  state  of 
liquidity.  It  is  urged  by  many  physicists,  though  not  by  all, 
that  it  has  become  solid  throughout,  as  solid  as  steel  or  glass ; 
the  conclusion  being  based  on  the  ground  that  if  liquid  within, 
the  crust  would  yield  with  the  earth's  rotation,  and  hence  the 
precession  of  the  equinoxes  arid  the  tides  of  the  ocean  would 
be  different  in  amount  from  what  they  actually  are.  It  seems 
to  be  evident  that  geological  facts  cannot  be  explained  on  the 
basis  of  absolute  solidity.  There  must  have  been  in  past 
time,  as  many  have  urged,  either  a  plastic  layer  between  the 

11 


162  DYNAMICAL    GEOLOGY. 

crust  and  a  solid  nucleus,  or,  at  least,  the  remains  of  such 
a  plastic  layer,  wherever  the  great  movements  have  taken 
place. 

But  it  is  stated  that  if  a  plastic  layer  exists,  and  the  crust 
above  it  is  thin,  —  say  twenty-five  miles,  —  the  crust  would 
rest  on  the  mobile  sea  underneath  it  like  a  floating  mass, 
the  earth's  surface  being  so  nearly  flat,  and  hence  it  would 
be  pressed  down  by  any  local  addition  to  its  weight,  however 
slight ;  that  it  could  not  sustain  mountain  elevations,  except 
the  lower  part  of  the  crust  beneath  the  mountain  were  flexed 
downward  as  the  upper  part  was  forced  upward,  so  as  to 
leave  a  vacant  space  between,  and  thus  make  a  float  for  the 
mountain  to  stand  on ;  and  it  is  held  by  some  to  be  mathe- 
matically demonstrated  that  a  protuberance  of  the  lower  part 
of  the  crust  must  necessarily  accompany  any  elevation  of  the 
upper  part  (Rev.  O.  Fisher).  It  lias  been  proved  also  that, 
in  the  case  of  a  crust  of  the  small  thickness  stated,  the  force 
from  contraction  and  the  gravity  of  the  crust  would  be  great 
enough  to  produce  all  the  inequalities  of  the  earth's  surface ; 
but  the  same  author  reaches  the  conclusion  that  only  a  small 
part  of  the  actual  inequalities  could  have  resulted  from  its 
action. 

It  seems  to  be  evident  that,  with  a  crust  so  mobile  as  above 
described,  the  lateral  pressure  generated  within  it  could  have 
produced  no  long  range  of  mountains,  under  one  common 
method  of  action ;  nothing  of  that  uniformity  of  results  ex- 
hibited in  many  great  regions  from  Archaean  time  onward ; 
no  mountain  borders  for  the  continents ;  no  general  system 
of  feature  lines  for  the  globe. 

The  facts  would  appear,  therefore,  to  prove  that  the  crust 
must  exceed  twenty-five  miles  in  thickness ;  must  be  thick 
enough  to  have  in  some  degree  the  virtues  of  an  arch,  and  yet 
not  so  thick  that  flexures  and  displacements,  und.er  the  condi- 
tions existing,  were  impossible.  The  demands  of  physical 
science  as  to  a  solid  globe  may  perhaps  be  met  by  assuming 
that  whatever  the  condition  of  the  plastic  layer  underneath 


MOVEMENTS  OF  THE  EARTH'S  CRUST.     163 

the  crust  in  past  time,  only  the  remains  of  it  now  exist,  the 
part  of  it  beneath  the  oceans  and  the  interiors  of  continents 
having  largely  disappeared  by  solidification. 


I.  Evolution  of  the  Earth's  Fundamental  Features. 

Although  it  is  not  proved  that  lateral  pressure  or  thrust  in 
the  crust,  resulting  from  slow  cooling,  was  actually  the  chief 
source  of  the  movements  in  mountain-making,  no  other  theory 
of  mountain-making  has  been  substituted  by  those  who  reject 
it.  Having,  consequently,  no  new  theory  to  present,  that 
based  on  contraction  from  cooling  is  here  explained. 

The  following  have  been  set  forth  as  the  different  steps  in 
the  evolution  of  the  earth's  features.  They  correspond  with 
the  fact  that  all  changes  in  the  progressing  earth  went  for- 
ward under  a  simple,  comprehensive  method  of  development. 

1.  The  Mountain-borders  of  the  Continents,  highest  and  most 
abounding  in  volcanoes  on  the  sides  of  the  largest  Ocean. — 
The  oceanic  area,  besides  being  much  depressed  below  the 
continental,  has  rather  abrupt  sides  to  the  true  oceanic  basin, 
as  explained  on  page  12.     The  lateral  pressure  in  the  crust 
being  universal  over  the  sphere,  the  force  in  the  oceanic  crust 
would  hence  have  acted  obliquely  upward  against  the  crust 
of  the  continental  border.     The  action  was  that  of  a  shove 
or  thrust  from  the  direction  of  the  ocean,  and  in  each  oceanic 
area  was  somewhat  proportional  to  its  extent ;  consequently, 
bendings,   uplifts,  fractures,  foldings  of  strata,  earthquakes, 
mountain-making,  became  eminently  features  of   the  conti- 
nental borders,  and  most  prominently  so  of  the  borders  which 
faced  the  largest  oceans. 

2.  Method  of  action,  and  its  progress  in  North  America. — 
The  two  systems  of  forces  engaged  in  the  progress  of  North 
America  were  those  from  the  direction  of  the  Atlantic  and 
the  Pacific   basins  —  the   latter   the   greatest.     Under  their 
action  the  V-shaped  Archsean  dry  land  (map,  page  199)  was 


164  DYNAMICAL  GEOLOGY. 

first  defined,  one  branch  stretching  northeastward  to  Labra- 
dor and  the  other  northwestward  to  the  arctic  seas,  and  thus 
facing  respectively  the  Atlantic  and  Pacific  areas,  while  moun- 
tains were  made  along  the  course  of  the  Appalachian  chain 
and  the  Blue  and  Highland  ridges.  It  follows,  from  the 
courses  of  the  arms  of  the  V,  and  of  the  mountains,  that  the 
Atlantic  force  acted  mainly  from  the  southeastward,  and 
the  Pacific  from  the  southwestward,  and  the  two,  therefore, 
nearly  at  right  angles  to  one  another.  It  is  also  apparent 
that  the  Pacific  force  even  then  was  the  greater,  and  hence 
the  Pacific  Ocean  the  larger ;  for  the  northwestward  branch 
of  the  V  is  far  the  longer. 

Thus  the  Archaean  nucleus  was  outlined,  and  the  position 
of  Hudson's  Bay  determined  within  the  arms  of  the  V-  From 
this  nucleal  dry  land  progress  went  forward  southeastward, 
or  toward  the  Atlantic,  and  southwestward,  or  toward  the 
Pacific,  successive  formations  being  added  under  gentle  oscil- 
lations, and  the  dry  land  gradually  extending  under  changes 
of  level  caused  mainly  by  the  same  forces.  Then,  when  the 
Lower  Silurian  closed,  appeared  the  Green  Mountains ;  and 
when  Paleozoic  time  was  closing,  appeared  the  Alleghany 
part  of  the  Appalachian  chain,  parallel  to  the  eastern  branch 
of  the  Archaean  heights.  Later  still  rose  the  trap  ridges  of 
the  Mesozoic  on  the  Atlantic  border  (p.  286  ),  making  an- 
other parallel  to  the  eastern  branch,  or  tripling  the  arm  of  the 
V  on  the  east,  and  even  repeating  all  the  bends  in  the 
Appalachians. 

Again,  on  the  Pacific  side,  other  ranges  were  made,  parallel 
to  the  course  of  the  Eocky  Mountain  chain  ;  among  them  — 
after  tlge  Jurassic  period,  the  Sierra  Nevada,  and,  after  the 
Cretaceous,  the  Wahsatch,  and  still  later,  Tertiary  ridges 
toward  the  coast,  each  epoch  adding  new  parallels  to  the 
western  branch  of  the  Archaean  nucleus.  Finally,  in  the 
course  of  the  Tertiary,  the  mass  of  the  Eocky  Mountains 
rose  to  its  full  height  above  the  ocean. 

Each  added  range,  as  is  seen,  proves  that  the  mountain- 


MOVEMENTS  OF  THE  EAKTH'S  CRUST.     165 

making  forces  continued  to  act  to  a  large  degree  from  the 
same  directions  as  in  Archaean  time. 

Thus,  the  continent  made  progress,  adding  layer  after  layer 
to  the  rocks  over  its  surface,  and  range  after  range  in  parallel 
lines  to  its  heights,  until  finally  the  continental  area  reached 
its  limit,  and  the  great  interior  basin  had  its  mountain-bor- 
ders completed :  on  the  east,  the  low  Appalachians,  and  the 
trap  ridges  of  the  Mesozoic  ;  on  the  west,  the  massive  and  lofty 
Rocky  Mountain  chain,  with  the  parallel  ranges  over  its 
western  slopes. 

It  is  explained  beyond  (on  page  373)  that,  when  the  con- 
tinent was  thus  far  completed,  there  occurred  a  change  in 
the  region  of  progress.  The  high-latitude  operations  of  the 
Quaternary  then  began. 

On  this  view,  the  evolution  of  the  features  of  the  surface 
went  forward  through  one  system  of  forces  originating  in  oue 
single  cause,  —  the  earth's  contraction  from  cooling.  North 
America,  which  is  here  appealed  to  for  explanations,  affords  the 
truest  and  clearest  illustration  of  the  principles  involved  in 
the  system  of  evolution,  because  it  lies  alone  between  the  two 
oceans,  the  Atlantic  and  Pacific,  with  the  nearest  continent, 
South  America,  to  the  east  of  its  meridians.  The  progress  on 
this  account  went  forward  with  great  regularity,  each  age 
repeating  the  preceding  in  the  direction  of  all  oscillations  or 
uplifts.  It  was  a  single  isolated  individual  making  system- 
atic progress  throughout  until  its  final  completion,  and  exhibits 
truly  the  system  in  the  earth's  development,  whatever  the 
true  theory  of  that  development.  Europe,  in  contrast,  has 
Africa  on  the  south  and  Asia  on  the  east ;  it  is,  therefore,  full 
of  complexities  in  its  feature  lines,  and  in  the  succession  of 
events  that  make  up  its  geological  history. 

2.  Formation  of  Mountain  Chains. 

1.  A  Geosyncline,  or  downward  bend  of  the  Crust,  the  first 
step  in  ordinary  Mountain-making.  —  In  the  making  of  the 


166  DYNAMICAL   GEOLOGY. 

Appalachians  there  was  first  a  slowly  progressing  subsidence ; 
it  began  in,  or  before,  the  Cambrian  or  Primordial  period,  and 
continued  in  progress  until  the  Carboniferous  age  closed.  As 
the  trough  deepened,  deposits  of  sediment,  and  sometimes  of 
limestone,  were  made,  that  kept  the  surface  of  the  region  near 
the  water  level ;  and,  when  the  trough  reached  its  maximum, 
there  were  at  least  30,000  feet  in  thickness  of  stratified  rock 
in  it  (page  277),  and  this,  therefore,  was  the  depth  of  the 
trough.  The  Green  Mountains  began  in  a  similar  subsidence, 
and  at  the  same  time;  and  the  trough  was  kept  full  with 
deposits  as  it  progressed  ;  but  it  reached  its  maximum,  or  the 
era  of  catastrophe,  at  the  close  of  the  Lower  Silurian.  Such 
facts  are  in  the  history  of  many,  if  not  all,  mountains. 

2,  The  bottom  of  the  Geosyncline  weakened  by  the  Heat  rising 
into  it  from  below.  —  As  planes  of  equal  temperature  within 
the  earth  have  a  nearly  uniform  distance  from  the  surface,  the 
accumulation  of  sedimentary  beds  in  a  sinking  trough  would 
occasion,  as   Herschel  long  since  urged,  the  corresponding 
rising  of  heat  from  below,  so  that,  with  30,000  feet  of  such 
accumulations,  a  given  isothermal   plane  would  have  been 
raised  30,000  feet.     Under   such  an  accession  of  heat,  the 
bottom  of  the  trough  would  have  been  greatly  weakened,  if 
not  partly  melted  off.     If  the  lower  surface  of  the  crust  had 
dipped  down  this  much   into  the  plastic  material  that  was 
beneath  it,  it  would  have   been   actually  melted  off.     The 
lateral   pressure,    acting   against    a   trough    thus   weakened, 
would  end,  as  has  been  suggested,  in  causing  a  collapse,  that 
is,  a  catastrophic  break  of  the  trough  below,  and  a  pressing 
together  of  the  stratified  beds  within  it.    And  with  this  break 
the  shaping  of  the  mountain  would  begin. 

3.  Character  of  the  Mountain  thus  made.  —  Under  such  cir- 
cumstances the  stratified  rocks  lying  in  the  geosyncline  or 
trough  would   be   folded,  profoundly  broken,  shoved  along 
fractures,  and  pressed  into  a  narrower  space  than  they  occu- 
pied before.     The  crust  beneath  was  that  of  the  geosyncline  ; 
and  lateral  pressure,  however  powerful,  could  not  possibly 


MOVEMENTS   OF   THE  EARTH'S   CRUST.  167 

have  given  an  upward  bend  at  the  time  to  the  downward 
Hexed  crust.  The  flexures  were  flexures  in  the  overlying 
strata ;  they  were  too  small  to  have  been  made  also  in  the 
thick  crust  on  which  the  strata  lay  (p.  160).  They  became 
unequal-sided,  as  represented  on  page  279,  and  the  mountain 
itself  inequilateral  (p.  159),  because  there  was  a  pushing 
side  in  the  mountain-making,  the  force  coming  mainly  from 
one  direction  (the  oceanic,  in  the  case  of  the  Appalachians). 
Faults  of  10,000  to  20,000  feet  were  among  the  effects,  be- 
cause the  crust  was  under  the  vast  pressure,  and  could 
break  in  oblique  planes,  where  it  could  not  bend ;  and  be- 
cause after  breaking,  it  would  continue  to  yield  and  thus  be 
shoved  up  or  down  along  the  plane  of  fracture.  Such  a 
mountain  range,  begun  in  a  geosyncline  and  ending  in  a 
catastrophe  of  displacement  and  upturning,  has  been  named 
a  synclinore,  it  owing  its  origin  to  the  progress  of  a  geosyn- 
cline. (The  word  is  from  the  Greek  for  syncline,  and  opos, 
mountain.) 

On  the  side  away  from  the  chief  source  of  movement,  and 
beyond  the  profoundest  faults,  the  elevations  that  have  taken 
place  have  commonly  made  vast  plateaus  of  nearly  horizontal 
beds,  like  the  Cumberland  mountain  region  of  Tennessee  and 
its  continuation  through  western  and  northern  Pennsylvania, 
to  the  Catskill  Mountain  plateau  of  southern  New  York,  on 
the  outskirts  of  the  Appalachian  range ;  and  the  Uintah 
Mountain  plateau  and  others  of  southern  Utah,  on  the  out- 
skirts of  the  Wahsatch  range.  In  such  elevated  areas,  several 
thousands  of  feet  above  the  sea  level,  and  of  wide  extent, 
running  waters  have  had  their  opportunity  for  sculpturing, 
and  have  thus  made  some  of  the  most  majestic  mountain 
groups  of  ridges  and  peaks  in  the  world.  In  Tennessee,  the 
region  of  great  folds  and  faults  directly  east  of  the  Cum- 
berland plateau  was  at  first,  beyond  doubt,  of  far  greater 
height  than  the  plateau  ;  but  owing  to  the  vast  amount  of 
fracturing  as  well  as  the  steep  slopes,  denudation  has  finally 
made  it  lower,  and  it  is  now  the  "Valley  of  East  Tennessee," 


168  DYNAMICAL    GEOLOGY. 

while  the  plateau  is  "  Cumberland  Mountain."     Not  less  was 
the  denudation  in  front  of  the  Catskill  plateau. 

4.  A  Mountain  Chain  may  comprise  ranges  of  different  epochs 
of  origin.  —  The  Appalachian  chain  consists  of  (1)  mountains 
of  Archaean  age ;  (2)  the  Green  Mountains,  that  date  from 
the  close  of  the  Lower  Silurian;   and  (3)  the  Alleghanies, 
that  were  formed  at  the  close  of  the  Carboniferous  age.     The 
Green  Mountains  began  in  the  same  great  geosyncline  with 
the  Alleghanies ;  but  that  part  reached  its  completion  first, 
probably  because  so  near  the  stable  Adirondack  border  of 
the  continent.     It  is  probable  that  the  Archaean  portion  of  the 
Appalachian   chain  —  which  includes  the   Blue   Kidge,  the 
New  Jersey  Highlands,  continued  in  Putnam  County,  N.  Y., 
some  areas  in  western  New  England,  and  the  Adirondacks,  — 
corresponds  to  another  older  synclinoro.     Thus  a  mountain 
chain  may  comprise  several  ranges,  made  at  widely  different 
epochs. 

5.  Metamorphism   and   other   attendant  effects.  —  The   heat 
developed  through  the  transformation  of  motion,  added  to 
that  rising  into  the  strata  from  below,  would  produce  all  the 
consolidation  and  crystallization  —  that  is,  all  the  metamor- 
phism  —  which  has  been  in  any  case  observed,  and  on  a  scale 
as  vast  as  that  of  the  mountain  range  so  developed.     It  gives 
a  full  explanation,  therefore,  of  the  origin  of  regional  meta- 
morphism. 

The  heat  might  be  sufficient  in  some  parts  to  reduce  a  rock 
to  a  plastic  state,  and  so  obliterate  all  its  original  bedding. 
One  result  of  this  would  be  to  make  a  massive  metamorphic 
rock,  like  granite,  in  place  of  gneiss  or  other  schistose  kind ; 
and  another  result,  if  the  overlying  rocks  were  fractured,  and 
so  fissures  opened  down  to  the  plastic  rock,  would  be  to  fill 
the  fissures  with  the  plastic  rock,  making  dike-like  veins  of 
granite,  or  of  other  material,  according  to  the  kind  of  rock  so 
fused.  It  might  possibly  give  a  long  core,  or  central  mass, 
of  granite  to  a  mountain-range,  —  a  condition  of  the  Sierra 
Nevada  which  has  been  attributed  by  some  to  this  cause. 


MOVEMENTS  OF  THE  EARTH'S  CRUST.     169 

6.  Slaty  cleavage,  jointed  structure.  —  Slaty  cleavar/e  has 
been  proved  by  experiments  to  result  whenever  fine-grained 
rock-material  is  subjected  to  pressure ;  and  to  be  due  to  the 
flattening  of  all  air-cells  and  compressible  particles,  and 
the  arranging  of  all  flat  grains  in  planes  at  right  angles  to 
the  pressure.  As  it  occurs  in  upturned  or  flexed  rocks  of  fine 
grain,  the  pressure  producing  upturning  or  flexure,  and  also 
mountain-making,  has  been  generally  the  cause.  It  conforms 
to  the  bedding  whenever  the  bedding  is,  as  a  consequence  of 
the  upturning,  at  right  angles,  or  nearly  so,  to  the  pressure. 

A  jointed  structure,  on  the  large  scale  observed  in  many 
regions,  has  been  another  result  of  the  slow  uplifting  or  flex- 
ing action  from  lateral  pressure.  The  strain,  after  accumu- 
lating through  a  long  period,  has  ended  in  fractures  of  great 
depth,  evenness,  and  general  parallelism,  at  right  angles  to 
the  direction  of  the  pressure,  and  often  also  in  a  subordinate 
system  of  fractures  transverse  to  it ;  sometimes  also  —  when 
a  warping  of  the  beds  was  likewise  in  progress  —  in  joints 
that  were  not  parallel.  Slowly  accumulating  pressure  from 
any  other  source  would  produce  like  results. 

In  many  quartzose  sandstones  the  grains  are  so  loosely 
coherent  that  the  vibrations  attending  any  upturning  and 
fracturing  tend  to  shake  out  all  traces  of  the  original  bedding. 
At  the  same  time,  the  lateral  pressure  produces  planes  of 
apparent  bedding  and  division  at  right  angles  to  its  direction, 
-  partly  as  a  result  of  the  strain  attending  the  movements, 
and  partly  owing  directly  to  the  pressure,  as  in  slaty  cleavage. 
Hence  quartzytes,  which  are  metamorphic  sandstones,  seldom 
retain  their  true  bedding,  but  have  nearly  vertical  divisional 
planes  instead. 

?.  Geanticlines  in  Mountain-making.  —  In  the  movements  of 
the  earth's  crust,  there  would  necessarily  be  upward  as  well 
as  downward  flexures,  —  that  is,  geanticlines  as  well  as  geo- 
synclines.  The  Appalachians,  as  explained  a.bove,  may,  when 
first  made,  have  stood  up  in  ridges,  without  having  under- 
gone any  uplifting  from  an  elevation  of  the  crust  underneath. 


170  DYNAMICAL  GEOLOGY. 

But,  however  this  may  be,  the  region  actually  experienced 
elevation  before  the  Triassic  period  opened,  as  is  proved  by 
the  position  of  the  Triassic  beds ;  and  this  took  place  prob- 
ably through  a  gentle,  upward  bending  of  the  crust,  such  a 
bending  becoming  possible  after  (although  not  before)  the 
region  of  the  Appalachians  had  been  made  a  portion  of  the 
stable  part  of  the  continent. 

The  Eocky  Mountains,  in  the  Cretaceous  era,  within  the 
area  of  the  United  States,  were  10,000  feet  below  their 
present  level,  the  sea  covering  them  (p.  323).  They  were 
raised  as  a  whole  during  the  Tertiary,  and  it  must  have  been 
through  a  low  geanticline.  While  the  Tertiary  mountains 
were  in  progress,  the  part  of  the  force  not  expended  in 
producing  them  appears  to  have  carried  forward  an  upward 
bend,  or  geanticline,  of  the  vast  Rocky  Mountain  region  as 
.a  whole. 

After  the  crust  had  become  thickened  by  the  earth's  inter- 
nal cooling,  through  the  ages,  and  had  been  stiffened  also  by 
the  plication  and  solidification,  and  partly  the  crystallization, 
of  the  strata,  geosynclinal  troughs  over  the  continents,  like  that 
of  the  Appalachian  region,  became  less  a  possibility ;  and  con- 
sequently the  chief  movement  caused  by  the  ever-continuing 
lateral  pressure  would  have  been  an  upward  one.  It  may  be 
for  this  reason  that  the  mountain-chains  received  their  great 
height  so  largely  in  the  Tertiary  ;  and  that  the  areas  over  the 
earth's  surface  that  were  affected  by  single  movements,  such 
as  the  high-latitude  movements  of  the  Quaternary,  were  so 
vast.  There  was,  also,  in  the  Quaternary,  if  Darwin's  view  as 
to  the  formation  of  coral  atolls  (that  presented  on  page  78)  is 
right,1  a  downward  bending  through  the  warm  parts  of  the 

1  Darwin's  theory  explains  completely  the  observed  facts  with  regard  to 
coral  formations.  But  it  assumes  the  fact  of  a  great  oceanic  subsidence,  which 
has  not  been  independently  proved.  It  has  been  suggested  that  shells  of 
Rhizopods  and  the  stony  secretions  of  other  forms  of  marine  life  may  have 
built  up  portions  of  the  sea-bottom  to  within  100  or  120  feet  of  the  surface  - 
the  depth  at  which  reef-corals  can  grow  — and  that  only  the  upper  120  feet 
consist  of  coraJ-reef  rock  ;  and,  in  order  to  account  for  the  open  interior, 


MOVEMENTS  OF  THE  EARTH'S  CRUST.    171 

oceans,  —  the  coral  island  subsidence,  —  affecting  an  area  in 
the  Pacific  over  5,000  miles  in  its  longer  diameter;  an  extent 
far  beyond  that  of  the  mountain-making  geosynclines  of 
earlier  time.  It  may  be  that  the  Pacific  coral-island  subsid- 
ence was  the  counterpart  of  the  geauticlinal  movement  over 
the  continents  of  the  later  Tertiary  and  early  Quaternary. 

8.  Fractures  and  outflows  of  igneous  rocks  most  numerous 
in  later  geological  times.  —  Great  floods  of  doleryte  and  trachyte 
were  poured  out  over  the  Kocky  Mountain  slope,  after  the 
close  of  the  Cretaceous  period.  The  previous  plications  and 
solidifications  of  the  strata  involved  in  the  making  of  the 
various  ranges  of  mountains  would  have  left  the  crust  firm 
and  unyielding  ;  and,  being  too  stiff  to  bend,  it  broke,  and 
hence  the  eruptions.  It  had  broken  at  times  before ;  but  at 
this  time  the  fractures  became  much  more  numerous,  and  the 
floods  of  rock  more  extensive.  Moreover,  from  this  era  ap- 
pears to  date  the  opening  of  the  great  volcanoes  of  the  Cascade 
range.  In  fact,  the  larger  part  of  the  volcanic  eruptions  of 
the  world  are  probably,  for  a  like  reason,  of  Tertiary  and  later 
origin. 

Such  are  the  general  steps  of  progress,  and  their  explana- 
tions, according  to  that  theory  of  mountain-making  which 
attributes  the  movement  to  a  lateral  thrust  in  the  earth's  crust 

or  lagoon,  of  the  coral  island,  it  is  further  supposed  that  the  structures  were 
begun  on  the  rims  of  submarine  craters. 

The  objections  to  this  theory  are  :  (1)  that  the  existence  of  craters  in  the 
lava  accumulations  made  by  submarine  volcanic  action  is  improbable  ;  (2)  that 
no  craters  of  known  volcanoes  have  even  approximately  the  size  of  many  of 
the  lagoons  of  atolls  ;  (3)  that  the  lagoons  are  never  circular,  but  as  irregular 
in  outline,  nearly,  as  the  other  islands  of  the  ocean  ;  (4)  that  in  the  Feejee 
group  all  the  steps  in  the  progress  of  an  atoll  assumed  in  the  Darwinian 
theory  are  exemplified,  from  the  high  volcanic  island  with  a  fringing  reef,  to 
the  atoll,  15  miles  in  diameter,  having  two  small  peaks  of  volcanic  rocks  in 
the  great  lagoon.  (See  map  of  the  Feejee  group  in  the  author's  "  Corals  and 
Coral  Islands,"  378  pp.  8vo,  New  York.)  A  few  borings  in  a  coral  island  to 
a  depth  of  500  or  1,000  feet,  with  a  drill  large  enough  to  give  a  core  six  inches 
in  diameter  for  examination,  would  settle  the  question  as  to  whether  the  rock 
below  is  of  coral-reef  origin  or  not. 


172  DYNAMICAL  GEOLOGY. 

• 

as  a  result  of  contraction  on  cooling.  The  universality  of 
system  in  the  features  of  continents  and  the  characters  of 
mountains  has  as  yet  no  other  probable  explanation.  Specu- 
lation has  appealed  to  the  power  of  crystallization  as  a 
determining  cause  for  at  least  the  direction  of  the  grand 
feature  lines.  But  of  this  there  is  too  much  uncertainty  for 
any  confidence  in  the  view. 

To  obtain  an  adequate  idea  of  the  slow  progress  of  the  earth 
in  the  making  of  its  mountains,  it  is  necessary  to  remember 
that  the  process  has  gone  on  only  after  immensely  long 
periods  of  quiet  and  gentle  oscillations.  After  the  beginning 
of  the  Cambrian,  the  first  period  of  disturbance  in  North 
America  of  special  note  was  that  at  the  close  of  the  Lower 
Silurian,  in  which  the  Green  Mountains  were  finished ;  and 
if  time,  from  the  beginning  of  the  Silurian  to  the  present,  in- 
cluded only  48  millions  of  years,  (p.  375)  the  interval  between 
the  beginning  of  the  Cambrian  and  the  uplifts  and  metamor- 
phism  -of  the  Green  Mountains  was  at  least  20  millions  of 
years.  Another  epoch  of  disturbance  was  that  at  the  close  of 
the  Carboniferous  era,  in  which  the  rocks  of  the  Alleghanies 
were  folded  up ;  on  the  above  estimate  of  the  length  of  time, 
it  occurred  about  thirty-six  millions  of  years  after  the  com- 
mencement of  the  Silurian  ;  so  that  the  Alleghanies  were  at 
least  36  millions  of  years  in  making,  the  preparatory  subsi- 
dence having  begun  as  early  as  the  beginning  of  the  Silurian, 
The  next  on  the  Atlantic  border  was  that  of  the  displace- 
ments of  the  Triassico-Jurassic  sandstone  and  the  accompany- 
ing igneous  ejections,  which  occurred  before  the  Cretaceous 
Pra?  —  at  least  five  millions  of  years,  on  the  above  estimate  of 
the  length  of  time,  after  the  Appalachian  revolution.  Thus, 
whatever  the  mountain-making  force,  an  exceedingly  long 
time  was  required  in  order  to  accumulate  a  sufficient  amount 
to  produce  a  general  yielding  and  plication  or  displacement 
of  the  beds,  and  start  off  a  new  range  of  prominent  elevations 
over  the  earth's  crust. 


ANIMAL  AND   VEGETABLE  KINGDOMS.  173 


REVIEW    OP    THE   ANIMAL    AND    VEGETABLE 
KINGDOMS. 

THE  following  pages  on  the  Animal  and  Vegetable  King- 
doms are  inserted  in  this  place  to  prepare  the  student 
for  the  following  portion  of  the  work,  on  Historical  Geology, 
in  which  the  progress  of  life  is  a  prominent  part. 

Distinctions  between  an  Animal  and  a  Plant. 

1.  An  Animal,  —  An  animal  is  a  living  being,  sustained  by 
nutriment  taken  into  an  internal  cavity  or  stomach,  through 
an  opening  called  the  mouth.     It  is  capable  of  perceiving  the 
existence  of  other  objects,  through  one  or  more  senses.     It 
has  (except  in  some  of  the  lowest  species)  a  head,  which  is 
the  chief  seat  of  the  power  of  voluntary  motion,  and  which 
contains   the   mouth.      It   is   fundamentally   a  fore-and-aft 
structure,  the  head  being  the  anterior  extremity,  and  it  is 
typically  forward-moving.     With  its  growth  from  the  germ, 
there  is  an  increase  in  mechanical  power  until  the  adult  size 
is  reached.     In  the  processes  of  respiration  and  growth,  it 
gives  out  carbonic  acid  and  uses  oxygen. 

2.  A  Plant.  —  A  plant  is  a  living  being  sustained  by  nutri- 
ment taken  up  externally  by  leaves  and  roots.     It  is  inca- 
pable of  perception,  having  no  senses.     It  has  no  head,  no 
power  of  voluntary  motion,  no  mouth.     It  is  fundamentally 
an  up-and-down  structure,   and,  with  few  exceptions,  fixed. 
In  its  growth  from  the  germ  or  seed,  there  is  no  increasing 
mechanical  power.     In  the  process  of  growth,  it  gives  out 
oxygen  and  uses  carbonic  acid. 


174  ANIMAL  KINGDOM. 


I.    Animal  Kingdom. 
I.    The  Animal   Structure. 

The  nature  of  an  animal  requires,  for  a  full  exhibition  of 
its  powers,  the  following  parts  :  — 

1.  A  stomach  and  its  appendages  to  turn  the  food  into 
blood,  with  an  arrangement  for  carrying  off  refuse  material. 

2.  A  system  of  vessels  for  carrying  this  blood  throughout 
the  body,  so  as  to  promote  growth  and  a  renewal  of  the 
structure. 

3.  A  heart,  or  forcing-pump,  to  send  the  blood  through  the 
vessels. 

4.  A  means  of  respiration,  or  of  taking  air  into  the  system 
(as  by  lungs  or  gills),  because  this  growth  and  renewal  re- 
quire the  oxygen  of  the  air  to  act  in  conjunction  with  the 
blood,  as  much  as  a  fire  requires  air  in  order  that  the  fuel 
may  burn. 

5.  Muscles,  or  contractile  fibres,  to  act  by  contraction  and 
relaxation  in  putting  the  parts  or  members  in  motion. 

6.  A  brain,  or  head-mass  of  nervous  matter,  and  a  system 
of  nerves,  branching  through  the  body,  to  serve  as  a  seat 
for  the  will  and  for  the  power  of  sensation  and  motion,  and 
to   convey  the   determinations    of    the   will  and   sensation 
through  the  body. 

In  the  lowest  form  of  animal  life,  as  some  microscopic 
Protozoans,  the  stomach  is  not  a  permanent  cavity,  but  is 
formed  in  the  mass  of  the  tissue  whenever  a  particle  of  food 
comes  in  contact  with  the  body.  In  other  words,  a  stomach 
is  extemporized  as  it  is  needed.  In  species  of  a  little  higher 
grade,  as  Polyps,  there  is  a  mouth  and  stomach,  with  mus- 
cles, an  imperfect  system  of  nerves  when  any,  and  a  means 
of  respiration  through  the  general  surface  of  the  body;  but 
there  is  no  distinct  heart,  and  the  animal  is  ordinarily  fixed 
to  a  support. 


ANIMAL   KINGDOM.  175 


2.    Subdivisions   of  the    Animal    Kingdom. 

Animals  (with  the  exception  of  some  inferior  species  for- 
merly referred  to  the  Articulates  and  of  little  geological 
importance)  have  been  divided  into  five  groups,  called  sub- 
kingdoms.  These  five  sub-kingdoms  are  the  following :  — 

7.  The  Vertebrate:  having  (as  in  Man,  Quadrupeds,  Birds, 
Reptiles,  and  Fishes)  an  internal  jointed  skeleton,  of  which 
the  backbone  is  called  the  vertebral  column,  and  each  of  its 
joints  a  vertebra  ;  and  a  bone-sheathed  cavity  along  the  back 
for  the  great  nervous  chord. 

The  remaining  sub-kingdoms  have  no  vertebral  skeleton  and 
are  called  Invertebrates. 

2.  The  Articulate:  having   (as   in    Insects,   Spiders,  Crabs, 
Lobsters,  Worms)  the  body  and  its  appendages  (as  the  legs, 
etc.)  articulated,  that  is,  made  up  of  a  series  of  joints. 

3.  The  Molluscan:    having  (as  in  the  Oyster,  Clam,  Snail, 
Cuttle-fish)  a  soft,  fleshy  body  without  articulations  or  joints, 
and  without  a  radiated  structure  ;  and  the  appendages,  when 
any  exist,  also  without  joints.     The  name  is  from  the  Latin 
moUis,  soft. 

4.  The  Radiate:  having  (as   in   the   Polyp,   Medusa,   Sea- 
urchin,  Star-fish)  the  body,  both  externally  and  internally, 
radiate  in  arrangement,  that  is,  having  similar  parts  or  organs 
repeated  around  a  vertical  axis,  —  as  in  a  flower  the  parts  are 
radiately  arranged  about  its  centre  or  central  axis. 

Those  Radiates  which  have  the  mouth  the  only  opening  to 
the  digestive  cavity  are  called  Coelenterates,  from  the  Greek 
for  hoUoiu  within.  They  include  all  Polyps,  together  with  the 
Medusae  and  other  Acalephs  (p.  184). 

5.  The  Protozoan.  —  Besides  the  above,  there  are  other  spe- 
cies of  so  extreme  simplicity  that  neither  of  the  systems  of 
structure  above  mentioned  is  apparent  in  them,  and  these  are, 
therefore,  in  a  sense  systemless  animals.     Many  have  not  even 
a  mouth.     They  include  the  Sponges,  and  also  a  large  number 
of  minute  species,  visible  only  with  the  aid  of  a  microscope. 


176  ANIMAL  KINGDOM. 

1.    Sub-kingdom  of  Vertebrates^ 

Class  1.  —  Mammals.  —  Warm-blooded  animals  that  suckle 
their  young,  as  Man,  Quadrupeds,  Whales.  Nearly  all  are 
viviparous;  a  few  (as  the  Opossum  and  other  Marsupials] 
are  semi-oviparous,  the  young  at  birth  being  very  immature, 
and  being  therefore  taken  into  a  pouch  (in  Latin  marsupium 
signifies  pouch)  where  they  draw  nutriment  from  the  mother 
until  matured. 

Class  2.  —  Birds.  —  Warm-blooded  air-breathing  animals, 
oviparous,  having  a  covering  of  feathers,  and  the  anterior 
limbs  more  or  less  perfect  wings. 

Class  3.  —  Reptiles.  —  Cold-blooded  air-breathing  animals, 
oviparous,  having  a  covering  of  scales  or  simply  a  naked  skin 
(as  Crocodiles,  Lizards,  Turtles,  Snakes) ;  they  breathe  with 
lungs  (or  are  air-breathing)  when  young  as  well  as  after- 
ward, being,  in  this  respect,  like  birds  and  quadrupeds. 

Class  4-  —  Amphibians  (as  Frogs  and  Salamanders),  which 
differ  from  true  Eeptiles  in  breathing  by  means  of  gills  when 
young,  and  afterward  becoming  air-breathing,  the  animal  un- 
dergoing, thus,  a  metamorphosis. 

Class  5.  —  Fishes.  — Cold-blooded  oviparous  animals,  breath- 
ing by  means  of  gills,  and  having  a  covering  of  scales  or  simply 
a  naked  skin.  Among  fishes  :  - 

1.  Teliosts  (as  the  Perch,  Salmon,  and  all  common  fishes) 
have  the  scales  usually  membranous,  the  skeleton  bony,  and 
the  gills  attached  at  only  one  margin. 

The  name  is  from  the  Greek  reXeto?  perfect,  and  ba-reov, 
lone,  alluding  to  the  skeleton  being  all  of  it  bony. 

The  scales  in  many  are  toothed  or  set  with  spines  about 
the  inner  margin  (Fig.  125),  wliile  others  have  the  margin 
smooth  (Fig.  124).  Fishes  having  scales  of  the  former  kind, 
as  the  Perch,  have  been  called  Ctenoids  by  Agassiz  (from  the 
Greek  /cre/9,  comb) ;  and  those  having  scales  of  the  latter 
kind,  as  the  Salmon,  etc.,  Cycloids  (from  the  Greek  /cvtcXos, 
circle). 

2.  Ganoids  (as   the   Gar-pike   and   Sturgeon),   having  the 


VERTEBRATES. 


Ill 


scales  bony  and  usually  shining,  and  the  skeleton  often  car- 
tilaginous.    The  name  is  from  the  Greek  ydvos,  shining. 

Fig.  120  represents  one  of  the  ancient  Ganoids.  The  verte- 
bral column  extends  to  the  extremity  of  the  tail,  so  that  the 
tail-fin  is  vertcbratcd,  while,  in  modern  Gars  and  Teliosts,  the 


Fig.  120. 


Palaeoniscus  Freieslebeni  (  x 


vertebral  column  stops  at  the  commencement  of  the  tail,  or 
the  tail-fin  is  non-vertebrate  (Fig.  121).    Agassiz  called  the 


Figs.  121-129. 
126. 


GANOIDS  (excepting  124,  125).  —Fig.  121,  Tail  of  Thrissops  (X  £) ;  122,  Scales  of  Cheiro- 
lepis  Traillii  (X  12);  123  Palseoniscus  lepidurus  (X  6) ;  123,  a,  under-view  of  same  ;  124, 
scale  of  a  Cycloid  ;  125,  id.  of  a  Ctenoid  ;  126,  Part  of  pavement-teeth  of  Gyrodus 
umbilicus ;  127,  Tooth  of  Lepidosteus  ;  128,  id.  of  a  Cricodus  ;  129,  Section  of  tooth  of 
Lepidosteus  osseus. 

former  kind  heterocercal,  and  the  latter  homocercal.  The  scales 
are  either  rhombic,  as  in  Figs.  121,  or  rounded.  Some  of 
these  rhombic  bony  scales  are  shown  also  in  Figs.  122,  123. 
The  teeth  (Figs.  127,  128)  often  have  a  folded  or  laby- 

12 


178 


ANIMAL   KINGDOM. 


rinthine  texture  within,  as  in  Fig.  129,  representing  a  part  of 
a  section  of  a  tooth  enlarged.  In  one  group,  the  Ganoids 
have  a  pavement  of  teeth  in  the  mouth,  as  in  Fig.  126. 

3.  Selachians  (as  the  Sharks  and  Rays),  having  a  hard  skin, 
called  sJiagreen,  often  rough  with  minute  points,  the  skeleton 


SELACHIANS.  —  Fig.  130,  Spinax  Blainvillii  (X  i) ;  131,  Spine  of  anterior  dorsal  fin, 
natural  size  ;  132,  Cestradon  Philippi  (x  I)  ;  133,  Tooth  of  Lamna  elegans  ;  134,  Tooth 
of  Carcharodon  angustidens  ;  135,  Notidanus  primigenius  ;  136,  Hybodus  minor  ;  137, 
Hyb.  plicatilis  ;  138,  Mouth  of  a  Cestracion,  showing  pavement-teeth  of  lower  jaw;  139, 
Tooth  of  xVcrodus  minimus  ;  140,  Tooth  of  Acrodus  nobilis. 

more  or  less  completely  cartilaginous,  and  the  gills  attached 
by  both  margins.  The  name  is  from  the  Greek  creXa^o?,  car- 
tilage. 

Fig.  130  represents,  much  reduced,  one  of  the  order  (a  Spi- 
nax), having  the  mouth,  as  usual,  on  the  under  surface  of  the 


ARTICULATES.  179 

head  and  remarkable  for  the  spine  before  each  of  the  back 
fins  :  one  of  the  spines  is  shown,  natural  size,  in  Fig.  131. 
Fig.  132  is  an  outline  of  another  Selachian,  of  the  genus  Ces- 
tracion,  living  in  the  vicinity  of  Australia,  peculiar  in  having 
the  mouth  at  the  extremity  of  the  head,  and  also  in  the  teeth 
of  the  mouth  having,  in  part,  the  form  and  appearance  of  a 
pavement,  as  shown  in  Fig.  138.  Figs.  133  to  137  are  teeth 
of  different  Selachians  related  to  the  Sharks;  and  Figs.  139, 
140,  pavement-teeth  of  Cestraciont  species.  The  Cestraciont 
Selachians  were  once  very  common,  but  the  tribe  is  now 
nearly  extinct. 

2.    Sub-kingdom  of  Articulates. 

Among  Articulates  there  are  three  classes;  one,  including 
the  species  adapted  to  live  on  land,  and  which,  for  this  pur- 
pose, breathe  by  means  of  air-vessels  branching  through  the 
body ;  and  two,  of  species  adapted  to  live  in  water,  and, 
therefore,  having  gills. 

7.  Land  Articulates,  or  the  class  of  INSECTEANS.  There  are 
three  orders  or  grand  divisions  of  Insecteans,  namely  :  1.  In- 
sects ;  2.  Spiders ;  3.  Myriapods  (or  Centipedes). 

2.  Water  Articulates,  including  the  two  classes  —  1.  CRUS- 
TACEANS (as  Crabs,  Lobsters,  etc.),  and  2.  WORMS. 

CRUSTACEANS. 

A  knowledge  of  the  principal  subdivisions  of  Crustaceans 
is  especially  important  to  the  student  in  geology.  There  are 
three  orders  :  — 

1.  The  Decapods,  or  IQ-footcd  species,  as  the  Crab  (Fig.  142), 
Lobster,  Shrimp. 

2.  The  Tetradecapods,  or  14-footed  species,  as  the  Sow-bay 
(Fig.  143),  found  in  damp  places  under  logs,  the  Sand-flea  in 
the  sands,  or  cast-up  sea-weed  of  a  beach  (Fig.  144),  etc. 

3.  The  Entomostracans,  or  inferior  species,  having  the  feet 
defective,  as  the  Cyclops  and  related  species  (Figs.  146,  147)> 
Daphnia,  Limulus  or  Horse-shoe,  and  the  Cypris  and  other 


180 


ANIMAL   KINGDOM. 


Ostracoids  (Fig.  149).  These  Ostracoids  are  generally  minute 
species,  having  a  shell  like  that  of  a  bivalve  Mollusk,  as  Fig. 
104  shows  ;  but  inside  of  the  shell,  instead  of  an  animal  like  a 


Figs.  141-150. 


ARTICULATES. —  1.  Worms:  141,  Arenicola  piscatorum,  or  Lob-worm  (x  J)-  2-  Crusts 
ceans :  142,  Crab,  species  of  Cancer ;  143,  au  Isopod,  species  of  Porcellio  ;  144,  an  Amphi- 
pod,  species  of  Orchestia  ;  145,  an  Isopod,  species  of  Scrolls  (x  2) ;  146,  147,  Sapphirina 
Iris,—  146,  female,  147,  male  (x  6) ;  148,  Trilobite,  Calymeue  Blnmenbachii ;  149,  Cythere 
Americana,  of  the  Ostracoid  family  (X  12) ;  150,  Anatifa,  of  the  Cirriped  tribe. 

clam,  there  is  one  more  like  a  shrimp,  with  jointed  legs.  The 
name  is  from  the  Greek  ocrrpafcov,  shell,  the  word  from  which 
oyster  is  derived. 

Among  JSntomostracans,  there  are  also  the  Barnacles  and 
other  Cirripeds,  one  of  which  is  represented  in  Fig.  150. 

Trilobites  (Fig.  148)  are  related  to  the  Limulus  or  "  Horse- 
shoe" among  the'  lower  Crustaceans.  The  tribe  is  inter-- 
mediate in  some  points  between  Crustaceans  and  Scorpions, 
It  is  now  extinct. 

3    Sub-kingdom  of  Mollusks. 

There  are  three  grand  divisions  or  classes  of  Mollusks :  — 

1.  Ordinary  Mollusks,  as  the  Clam,  Snail,   and   Cuttle-fish, 
which  have  branchiae  (gills). 

2.  Ascidian  Mollusks,  which  have  no  branchiae  and  no  dis- 
tinct tentacles  or  arms,  and  which  have  only  a  leathery  or  mem- 
branous exterior,  and  therefore  are  not  found  among  fossils. 

3.  Brachiate  Mollusks,  which  have  two  or  more  tentacles  or 


MOLLUSKS. 


181 


arms,  with  no  branchiae,  and  which  are  usually  attached  by 
a  stem ;  many  of  which  have  two  arms  and  a  bivalve  shell, 
and  others  a  circle  or  spiral  of  tentacles  or  arms  and  thus  re- 
semble flowers  (Figs.  159, 160),  though  not  radiate  internally 
like  true  Eadiate  animals. 

1.  Ordinary  Mollusks,  —  These  are  of  three  orders  :  — 
7.  Cephalopods :  having  the  head  surrounded  by  arms,  and 
large  eyes ;  the  shell,  when  any  exists  as  an  external  covering 
for  the  body,  is,  with  a  rare  exception,  divided  internally  by 


Figs.  151-160. 


MOLLUSKS.  —  1.  Cephalopods  :  Fig.  151,  Nautilus,  showing  the  partitions  in  the  shell  and 
the  animal  in  the  outer  chamber,  —  2.  Gasteropoda:  152,  Helix.  — •  3.  Pteropods  :  153,  Cleo- 
dora.  —  4.  Conchifers:  154,  155,  156,  the  last,  the  oyster.  —  5.  Bracldopods :  157,  Lingula, 
on  its  stem  ;  158,  Terebratula,  showing  the  aperture  at  l>,  from  which  the  stem  for  attach- 
ment passes  out.  — 6.  Bryozoans :  159,  Eschara,  with  the  animals  a  little  enlarged  ;  160, 
one  of  the  animals  out  of  the  shell,  more  enlarged. 

cross-partitions  into  a  series  of  chambers,  whence  they  are 
called  chambered  shells,  as  in  the  Nautilus  (Fig.  151)  and  Am- 
monite (page  296).  A  few  have  an  internal  chambered  shell ; 
others  an  internal  straight  bone,  which  has  sometimes  a  coni- 
cal cavity.  The  name  is  from  the  Greek  /c€(f)a\rj,  head,  and 

TTOl)?,  foot. 

2.  Cephalates :  havfng  a  head  with   distinct  eyes,  but   no 
arms  around  it,  and  usually  a  spiral  shell,  if  any;   as  the 


182  ANIMAL  KINGDOM. 

Snail  (Fig.  152)  and  other  Univalves.  The  species  of  one 
division  —  that  containing  the  Snail  and  all  ordinary  Uni- 
valves—  are  called  Gasteropods,  from  the  Greek  yac-ri'ip  and 
Trot)?,  implying  that  they  crawl  on  their  ventral  surface, — 
this  part  acting,  therefore,  as  a  foot.  In  another  division,  they 
have  a  pair  of  wing-like  oars  for  swimming,  and  these  are 
called  Pteropods  (Fig.  153),  from  the  Greek  Trre/ooV,  wing,  and 
TTOU?,  foot. 

3.  Acephals  (from  a,  without,  and  /fe<£aXrJ,  head} :  having  no 
prominent  head,  and  only  imperfect  eyes,  if  any ;  and  the 
shell  commonly  of  two  parts  called  valves,  placed  either  side 
of  the  body,  whence  the  common  name  of  most  of  the  species, 
Bivalves;  as  the  oyster,  clam  (Figs.  154-156).  These  species 
are  called  Lamellibranchs,  because  they  have  thin  lamellar 
gills  either  side  of  the  body,  from  lamella,  a  plate,  and  branchia, 
a  gill.  The  body  has  on  either  side  a  thin  fold  of  ^kin  called 
the  pallium,  or  cloak. 

In  Fig.  154,  showing  the  inside  of  a  valve,  1,  2  are  impres- 
sions of  the  two  great  muscles  by  which  the  animal  closes  the 
shell,  and  p  p  is  the  impression  of  the  margin  of  the  mantle 
or  pallium,  called  the  pallial  impression.  This  mantle  lies 
next  to  the  shell,  and  the  shell  is  secreted  by  it ;  the  gills 
are  between  it  and  the  body  of  the  Mollusk.  In  Fig.  155, 
the  pallial  impression  p  p  has  a  deep  bend  or  sinus  opening 
toward  the  back  margin  of  the  valve.  Shells  having  this 
sinus  in  the  impression  are  described  as  sinupallial,  and  those 
without  it  as  integripallial.  In  Fig.  156,  of  the  oyster,  there 
is  but  one  large  muscular  impression  (at  2). 

2,  Brachiate  Mollusks.  —  These  are  of  two  orders  :  — 

7.  Brachiopods :  species  (Figs.  157>  158)  having  a  bivalve 
shell,  like  the  Lamellibranchs,  but  one  of  the  vah^es  dorsal 
(or  over  the  back),  and  the  other  ventral,  instead  of  being  on 
the  sides  of  the  body ;  moreover,  the  form  is  symmetrical 
either  side  of  a  middle  line ;  that  is,  if  a  line  be  dropped 
from  the  beak  to  the  opposite  edge  (as  from  I  to  a  in  Fig. 
158),  the  parts  of  the  shell  on  the  two  sides  of  the  line  will 


RADIATES. 


183 


b«  equal.  A  line  similarly  drawn  in  the  Lamellibranchs 
divides  the  valve  unequally  (as  in  Fig.  154).  The  animals 
have  two  spiral  arms  within,  which  serve  as  gills.  The 
name  BracMopod,  from  the  Greek  /8/oa^tW,  arm,  and  TTOVS, 
foot,  refers  to  these  arms. 

2.  Bryozoans:  species  of  minute  size  like  a  polyp  in  exter- 
nal form,  making  often  cellular  corals  which,  though  often  in 
thin  plates  or  incrustations,  sometimes  delicately  branch  like 
a  moss,  whence  the  name,  from  the  Greek  ftpvov,  moss,  and 
£a>ov,  animal.  They  include  the  Cellepores,  Flustras,  etc.  Fig. 
159  shows  a  number  of  the  animals  protruded  from  their  cells. 

4.    Sub-kingdom  of  Radiates. 

There  are  three  grand  divisions  of  Kadiates  :  — 


Figs.  161-170. 


RADIATES  —  1.  Echinoderms :  161,  Echinus,  the  spines  removed  from  half  the  surface 
(X  3);  162,  Star-fish,  Paleaster  Niagarensis  ;  163,  Crinoid,  Encrinus  liliiformis  ;  164,  Cri- 
noid,  of  the  family  of  Cystideans,  Calloeystites  Jewettii.  —  2.  Acalephs :  165,  a  Medusa, 
genus  Tiaropsis  ;  166,  Hydra  (x  8)  ;  167,  Syncoryna.  —3.  Polyps  :  Fig.  168,  an  Actinia; 
169,  a  coral,  Dendrophyllia  ;  170,  part  of  a  branch  of  a  coral  of.  the  genus  Gorgonia,  show- 
ing one  of  the  polyps  expanded. 

1.  Echinoderms  (Figs.  161  to  164):  having  a  more  or  less 
hard,  inflexible  exterior,  which  is  often  covered  with  spines,  — 


184  ANIMAL  KINGDOM. 

whence  the  name,  from  e^o>o?,  a  hedgehog,  and  Sep/ia,  skin. 
The  mouth  opens  downward  in  all  species  except  in  some  at- 
tached species.  Among  them  are :  7.  Echinoids,  in  which 
the  exterior  is  a  solid  shell  covered  with  spines,  and  the 
mouth  opens  downward  (Fig.  161  —  the  spines  are  removed 
from  half  of  the  shell) ;  2.  The  Asteriolds,  or  Star-fshes,  in 
which  the  exterior  is  rather  stiff,  but  still  flexible,  so  that  the 
animal  flexes  it  in  its  movements  (Fig.  162)  and  the  viscera 
extend  into  the  arms ;  3.  The  Crinoids  (including  the  Coma- 
tulids),  having  flexible  arms  like  star-fishes,  but  the  rays  and 
body  made  of  closely  fitting  solid  calcareous  pieces,  and  hav- 
ing in  the  Comatulids  arms  for  attachment,  and  in  the  other 
Crinoids  a  stem  and  being  thus  plant-like. 

Other  kinds  are  the  Holotliurwids,  which  are  much  like  the 
Echinoids  in  interior  structure  and  the  absence  of  arms,  but 
have  no  hard  exterior  shell,  and  are  seldom  found  fossil ;  and 
the  Ophiuroids,  or  Serpent-stars,  which  are  near  the  Asteroids, 
but  have  the  arms  very  slender,  with  no  groove  beneath. 

2.  Acalephs  (Figs.  165  - 167) :  having  a  soft,  flexible  body, 
usually  of  a  jelly-like  aspect,  though  rather  tough,  and  mov- 
ing, when  free,  with  the  mouth  downward,  as  the  Medusa 
(Fig.  165).      Some  of  the  species  called  Hydroid  Acalephs 
(Figs.  166, 167),  in  one  of  their  stages,  if  not  through  all,  look 
like  Polyps ;  and  some  of  these  Acalephs  form  corals,  like  the 
Polyps.     The  Millepores  are  Acaleph  corals.     The  other  spe- 
cies are  mostly  too  soft  to  be  common  as  fossils. 

3.  Polyps  (Figs.  168-170) :  having  a  soft  body  usually  at- 
tached to  a  support ;  a  mouth  opening  upward ;  one  or  more 
rows  of  tentacles  arranged  about  the  margin  of  a  disk  (some- 
what like  the  petals  of  an  Aster  around  its  central  disk) ;  and 
the  mouth  situated  at  the  centre  of  the  disk,  as  in  Fig.  168. 
Most  corals  are  made  by  polyps.    The  coral  is  secreted  within 
the  polyp  in  the  same  manner  as  bones  are  secreted  within 
other  animals.      Figs.  169,  170   represent  portions  of  living 
corals  with  the  polyps  expanded.     The  number  of  rays  in  the 
cells  of  many  modern  corals  (the  Actinoids)  is  a  multiple  of 


PROTOZOANS.  185 

six ;    and  that  in  many  of  the  more  ancient  corals,  those 
called  Cyatliophylloiil*,  is  a  multiple  of  Jour. 

5.   Protozoans. 

The  subdivisions  of  Protozoans  of  geological  importance 
are  those  of  the  Sponges  and  Ehizopods. 

1.  Sponges.  —  A  sponge  is  an  assemblage  of  minute  Proto- 
zoans produced  by  growth  from  a  single  germ.  The  united 
animals  secrete  the  horny  fibre,  and  also,  from  an  inner 
layer,  its  siliceous  spicules  (see  p.  67),  when  these  are  present. 
In  many  the  siliceous  portion  predominates ;  and  in  some 
tp.  314)  the  skeleton  is  wholly  of  silica. 

Fig.  171. 


Globigerina  bulloides. 

2.  Rhizopods.  —  PJiizopods  are  so  called  from  the  Greek  for 
root-like  feet,  because  of  the  slender,  thread-like  appendages 
(pseudopodia,  false  feet)  which  in  many  species  are  made  as 
they  are  protruded ;  they  serve  for  taking  food,  and  often  also 
for  digesting  it.  Those  of  special  interest  geologically  are  of 
two  groups. 

1.  Foraminifers,  which  have  calcareous  shells  (p.  65),  made 
up  usually  of  a  group  of  cells  spirally  or  alternately  arranged 


186 


VEGETABLE   KINGDOM. 


(Figs.  71  to  84,  p.  66).  The  shells  have  minute  pores  (fora- 
mina) through  which  the  threads  are  protruded.  Fig.  172 
represents  a  living  species  much  enlarged,  with  its  pseudo- 
podia  extended  ;  and  Fig.  171  the  common  Globigerina  of 
the  sea-bottom,  also  greatly  enlarged ;  when  alive  and  un- 
mutilated,  the  latter  has  its  shell  covered  with  spines,  as  in 
the  figure,  and  its  pseudopodia  protruded  along  the  spines 
(Wyville  Thomson). 

2.  Itadiolarians   (or   Polycystines),    which   have    siliceous 
shells,  as   explained  and  illustrated  on  page  67.     Fig.   173 


Fig.  172. 


Fig.  173. 


Fig.  172,  Rotalia,  living  Rliizopod  with  pseudopodia  protruded  ;  173,  Xiphacantha  X  50, 

a  Radiolarian. 

represents  another  species  which  has  radiating  spines;  al- 
though minute,  it  has  some  resemblance  to  the  glass  sponges. 
In  these  species  the  protoplasmic  animal  mass  (absent  in  thd 
figures)  is  collected  about  the  centre,  and  from  it  the  pseudo- 
podia  radiate  outward. 


II.  Vegetable  Kingdom. 

The  two  most  prominent  subdivisions  of  Plants  are  those 
of  (1)  Cryptogams  and  (2)  Phenogams. 

The  CRYPTOGAMS,  or  Flowerless  plants,  have  no  true  flowers, 
and  hence  the  name  from  the  Greek  (tcpvjrro^  and  yapo?), 
referring  to  the  concealed  method  of  fructification.  They 


CRYPTOGAMS. 


187 


comprise  the  Seaweeds,  Mosses,  Ferns,  etc.  They  produce 
spores  in  place  of  true  seeds,  the  spore  being  a  simple  cellule, 
while  true  seeds  have  about  the  germ-cellule  more  or  less  of 
albumen  and  starch  for  the  nutriment  of  the  embryo  plant. 

The  PHENOGAMS,  or  Floweriny  plants,  the  term  from  the 
Greek  (fyaivw  and  7^09),  referring  to  the  open  method  of 
fructification ;  that  is,  by  means  of  stamens  and  pistils,  the 
central  organs  in  flowers.  All  plants  are  here  included  that 
have  flowers,  from  the  grasses  to  the  ordinary  forest  trees. 

I.  Cryptogams.  —  The  lower  Cryptogams  consist  of  cellular 
tissue  alone;  the  higher,  like  Phenoganis,  of  both  woody 
fibre  and  cellular  tissue. 

Lower  Cryptogams  of  the  following  kinds  (A)  have  no  leafy 
stems:  (1)  Alya,  or  Seaweeds,  embracing  all  flowerless  and 
leafless  water  plants;  (2)  Funyi,  or  the  mushrooms,  mould, 
etc. ;  (r>)  Lichens,  the  dry  gray -green  and  gray  to  brown  and 
black  plants,  growing  in  dry  places,  and  often  covering  stones 
and  the  bark  of  trees.  An  exposed  rocky  bluff  usually  owes 
its  color  mostly  to  the  lichens  which  cover  it,  and  not  to  the 
rock  constituting  it.  The  follow- 
ing among  the  lower  Cryptogams 
(B)  have  leafy  stems:  (1)  Mosses, 
and  (2)  the  Liverworts. 

To  the  Alga3  belong  the  micro- 
scopic Diatoms  and  Desmi'h,  which 
are  one-celled  (unicellular)  plants, 
living  in  both  fresh  and  salt  water. 
The  Diatoms  (Figs.  174-179,  and 
88,  p.  68)  are  siliceous,  as  already  DIATOMs  highly 
explained.  The  Desmids  are  green, 
secrete  no  silica,  and  are  often 
found  fossil  in  flint  and  chert 
(Figs.  241-247,  p.  234).  They 
include  also  the  calcareous  Nullipores  (p.  66),  and  semi- 
calcareous  Corallines;  and  also  the  microscopic  Coccoliths 
and  Ehaldoliths  (p,  66). 


Figs.  174-179. 


magnified  ;  174,  Pin- 
nularia  peregrina  ;  175,  Pleurosigma 
angulatum  ;  176,  Actiuoptychussena- 
rius  ;  177,  a,  Melosira  sulcata  ;  178, 
Giammatophora  marina  :  179,  Baril- 
ar'a  paradoxa. 


188 


VEGETABLE    KINGDOM. 


Higher  Cryptogams.  —  These  Cryptogams,  having  bundles  of 
woody  tissue  in  the  stems,  are  called  Acrogens,  (from  the 
Greek  afcpov,  top,  and  yevvda),  I  grow)  because  they  grow 
upward  and  make  stems,  and  in  some  cases  high  trees. 

Acrogens  are  divided  into  (1)  Ferny;  (2)  Lywpods,  or 
Ground-pines ;  and  (3)  Equiwta,  or  Horsetails.  Some  tropical 
ferns  are  trees  10  to  30  feet  high,  having  a  broad  star  of  large 
fronds  at  tli3  top.  Ground-pines  have  the  foliage  of  minia- 
ture spruces  or  pines,  and  hence  the  name.  In  a  former  age 
they  grew  into  trees  40  feet  or  more  in  height,  closely  resem- 
bling in  aspect  modern  spruces  or  pines.  The  modern  Equi- 
seta  (sometimes  called  scouring-rushes)  are  slender  plants 
with  hollow  stems,  a  little  rush-like  in  habit.  The  stems 
are  jointed,  and  the  divisions  are  easily  broken  apart  at  the 
joints.  Ancient  species,  called  Calamites  (because  of  their 
reed-like  form,  from  the  Greek  /caXa/^o?,  reed),  were  10  to  20 
feet  high. 

II.  Phenogams.  —  Phenogams,  or  Flowering  plants,  are 
divided  into  two  sections,  according  to  the  mode  of  growth. 
(1)  The  Exogens  (so  named  from  the  Greek  ef&>,  outward,  and 
yevvdo),  I  groiv)  have  a  bark  separable  from  the  wood,  and 
grow  by  the  addition  of  a  layer  to  the  adjoining  surfaces  of 

the  bark  and  wood  each 

Figs.  180-183. 
182 


l.So 


year,  so  that  in  a  trans- 
verse section  of  a  stem 
there  are  rings  of  growth 
(Fig.  180)  marking  the 
age  of  the  stem.  They 
include  all  our  common 
trees  and  shrubbery  and 
a  large  part  of  smaller 
plants.  (2)  The  Endogens 
(so  named  from  evBov, 
within t  and  yevvdw),  have 
no  proper  bark,  and  show 
in  a  transverse  section  of  the  stem  the  ends  of  bundles  of 


Fig.  180,  section  of  exogenous  stem  ;  181,  id.  of  endo- 
genous ;  182,  fibres  of  the  Conifer,  Pinus  Strobus, 
showing  dots,  magnified  300  times ;  183,  same  of 
Araucaria  Cunningham!. 


PHENOGAMS.  189 

fibres  of  woody  tissue  with  more  or  less  of  spongy  cellular 
tissue  (Fig.  181).  They  grow  by  additions  to  the  bundles 
of  woody  fibre,  progressing  from  the  exterior  toward  the 
centre.  They  include  the  paliux,  rattan,  reed,  grasses,  indian 
corn.  When  the  bundles  of  fibres  in  a  palm  have  reached  the 
centre,  the  juices  can  no  longer  ascend,  and  the  plant  dies. 
Phenogams  are  divided  into  the  following  groups :  — 

1.  Grymnospenns  (from  ryv/juvos,  naked,  and  ajr^r^a,  seed}. 
—  Growth  exogenous ;  the  flowers  exceedingly  simple,  there 

being  only  one  or  two  stamens,  and  the  seed  naked,  —  the  seed 
in  many  species  being  on  the  inner  surface  of  the  scales  of 
cones ;  as  the  Pine,  Spruce,  Hemlock,  etc.  The  Gymnosperms 
include  (1)  the  Conifers,  or  the  Pine-tribe  of  plants,  usually 
called  evergreens;  and  (2)  the  Of/cads,  or  plants  related  to 
the  Ct/cas  and  Zamia,  which  have  the  leaves  of  a  Palm  (page 
288),  although,  in  fruit  and  wood,  true  Gymnosperms. 

The  wood  of  the  Conifers  is  simply  woody  fibre  without 
ducts,  and  in  this  respect,  as  well  as  in  the  naked  seed  and 
very  simple  flowers,  this  tribe  shows  its  inferiority  to  the  fol- 
lowing subdivision.  The  fibres  of  Coniferous  wood  may  be 
distinguished,  even  in  petrified  specimens,  by  the  dots  (Fig. 
182)  along  their  surface,  as  seen  under  a  high  magnifier.  The 
dots  look  like  holes,  though  really  only  thinner  spaces.  In 
one  division  of  the  Conifers,  called  the  Araucarice,  of  much 
geological  interest,  these  dots  are  alternated  (Fig.  183). 

2.  Anyiospcrms  (from  dyyelov,  vessel,  and  (TTrcp/jia,  seed). — 
Growth  exogenous ;  the  seed  covered  or  contained  in  a  seed- 
vessel;  as  the  Maple,  Elm,  Apple,  Rose,  and  most  of  the  or- 
dinary shrubs  and  trees. 

3.  Endogcns.      Growth  endogenous,   as  above  explained. 
The  flowers  of  Endosens  include  some  of  the  most  beautiful 

O 

kinds,  as  those  of  the  Lily  tribe,  Orchids,  etc. ;  and  the  edible 
products  exceed  in  value  those  of  all  other  plants,  —  grasses 
with  wheat,  indian  corn,  and  other  grains,  being  included, 
as  well  as  the  fruits  of  several  kinds  of  palm,  banana,  pine 
apple,  and  other  species. 


PART  IV 

HISTORICAL    GEOLOGY. 


HISTORICAL  GEOLOGY  treats  of  the  order  of  succession  in 
the  strata  of  the  earth's  crust,  and  of  the  changes  that  were 
going  on  during  the  formation  of  each  bed  or  stratum,  —  that 
is,  of  the  changes  in  the  oceans  and  the  land ;  of  the  changes 
in  the  atmosphere  and  climate ;  of  the  changes  in  the  plants 
and  animals.  In  other  words,  it  is  an  historical  view  of  the 
events  that  took  place  during  the  earth's  progress,  derived 
from  the  study  of  the  successive  rocks.  It  is  sometimes 
called  stratigrapfiical  geology;  but  this  term  embraces  only 
a  description  of  the  nature  and  arrangement  of  the  earth's 
strata. 

By  using  the  means  for  determining  the  order  of  the  sev- 
eral formations  mentioned  on  page  58,  and  by  a  careful  study 
of  the  organic  remains  (as  fossils  are  often  called)  contained 
in  the  rocks,  from  the  oldest  to  the  most  recent,  it  has  been 
found  that  a  number  of  great  ages  in  the  progress  of  this  life, 
and  in  other  events  of  the  history,  can  be  made  out. 

The  following  have  thus  been  recognized  :  — 

1.  There  was  first  an  age,  or  division  of  time,  when  there 
was  no  life  on  the  globe ;  or,  if  any  existed,  this  was  true 
only  in  the  later  part  of  the  age,  and  the  life  was  probably 
of  the  very  simplest  kinds. 

2.  There  was  next  an  age  when  Shells  or  Mollusks,  Corals, 
Crinoids,  and  Trilobites  abounded   in  the  oceans    when  the 


SUBDIVISIONS  IN   THE  HISTORY.  191 

continents  were  almost  all  beneath  the  salt  waters,  and  when 
there  was,  throughout  its  larger  part,  as  far  as  fossils  show,  no 
fishes  and  no  terrestrial  life. 

3.  There  was  next  an  age  when,  besides  Shells,  Corals, 
Crinoids,   Trilobites,   and  Worms,  Fishes  were  numerous  in 
the  waters,  and  when  the  lands,  though  yet  small,  were  more 
or  less  covered  with  vegetation. 

4.  There  was  next  an  age  when  the  continents  were  at 
many  successive  times  largely  dry  or  marshy  land,  and  the 
land  was  densely  overgrown  with  trees,  shrubs,  and  smaller 
plants,  of  the  remains  of  which  plants  the  great  coal-beds 
were  made.     In  animal  life  there  were,  besides  the  kinds 
already    mentioned,    various    Amphibians    and    some    other 
Reptiles  of  inferior  tribes. 

5.  There  was  next  an  age  when  Reptiles  were   exceed- 
ingly abundant,  far  outnumbering  and  exceeding  in  variety, 
and  many  also  in  size  and  even  in  rank,  those  of  the  present 
day. 

6.  There  was  next  an  age  when  the  Reptiles  had  dwindled, 
and  Mammals  or  Quadrupeds  were  in  great  numbers  over  the 
continents. 

7.  After  this  came  Man;  and  the  progress  of  life  here 
ended. 

The  above-mentioned  ages  in  the  progress  of  life  and  the 
earth's  history  have  received  the  following  names  :  — 

1.  Archaean  Time  or  Age.  —  The  name  is  from  the  Greek 
for  beginning. 

2.  Age  of  Invertebrates,  or  the  Silurian  Age. 

3.  Age  of  Fishes,  or  the  Devonian  Age. 

4.  Age  of  Coal-Plants,  or  the  Carboniferous  Age. 

5.  Age  of  Reptiles,  or  the  Reptilian  Age. 

6.  Age  of  Mammals,  or  the  Mammalian  Age. 

7.  Quaternary  Age,  or  the  Age  of  Man. 

The  first  of  these  ages — the  Arcliccan — stands  apart  as  pre- 
paratory to  the  age  of  Invertebrates,  or  the  Silurian,  when  the 
systems  of  life,  excepting  the  Vertebrate,  were  well  displayed. 


192  HISTORICAL  GEOLOGY. 

The  Silurian,  Devonian,  and  Carboniferous  ages  were  alike  in 
many  respects,  —  especially  in  the  aspect  of  antiquity  pervad- 
ing the  tribes  that  then  lived,  the  shells,  crinoids,  corals,  fishes, 
coal-plants,  and  reptiles  belonging  to  tribes  that  are  now  wholly 
or  nearly  extinct.  The  era  of  these  ages  has,  therefore,  been 
appropriately  called  Paleozoic  time,  the  word  Paleozoic  corning 
from  the  Greek  vraXato?,  ancient,  and  £o>7/,  life. 

The  next  age  was  ushered  in  after  the  extinction  of  many 
of  the  Paleozoic  tribes  ;  and  its  own  peculiar  life  approxi- 
mated more  to  that  of  the  existing  world.  Yet  it  was  still 
made  up  wholly  of  extinct  species,  and  the  most  prominent 
of  the  tribes  and  genera  disappeared  before  or  at  its  close. 
This  age  corresponds  to  Mediaeval  time  in  geological  history, 
and  is  called  Mcsozoic  time,  from  the  Greek  /u-eicro?,  middle,  and 
£0)77,  life. 

The  next  age,  as  well  as  the  last,  was  decidedly  modern  in 
the  aspect  of  its  species,  the  higher  as  well  as  lower.  Both 
are  included  under  the  division  called  Cenozoic  time,  from  the 
Greek  /rati^o?,  recent,  and  £0)77,  life  (the  ai  of  Greek  words 
always  becoming  e  in  English,  —  as,  for  example,  in  ether, 
from  the  Greek  alOr/p). 

The  following  are,  then,  the  grand  divisions  of  geological 
time  adopted :  — 

I.  Archaean  Time. 

II.  Paleozoic  Time,  including,  1.  The  Age  of  Invertebrates, 
or  Silurian;  2.  The  Age  of  Fishes,  or  Devonian;  3.  The  Age  of 
Coal- Plants,  or  Carboniferous. 

III.  Mesozoic  Time,  including  the  Reptilian  Age. 

IV.  Cenozoic  Time,  including  the  Tertiary  and  Quaternary 
Ages. 

The  following  sections  represent  the  successive  formations 
of  the  globe,  arranged  in  the  order  of  time,  with  the  subdi- 
visions corresponding  to  the  Ages  and  Periods. 


AGES. 


SUBDIVISIONS  IN  THE  HISTORY.  193 

Fig.  184.  —  PALEOZOIC.         AMERICAN  PERIODS.  FOREIGN  SUBDIVISIONS. 


Wenlock  beds. 
Upper  Llandovcry. 


Caradoc  sandstone. 
Bala  limestone. 
Llandeilo  group. 


T«AvV</A»XTrr\'uVH  I-  Archaean, 


Arcluean 


194  HISTORICAL  GEOLOGY. 

AGES.        Fig.  184.  (continued).  PERIODS  FOREIGN  SUBDIVISIONS. 


Recent. 

Champlain. 

Glacial. 


Recent. 


Quaternary,  or 
Pleistocene. 


Pliocene. 
Miocene. 
Eocene. 


Upper  Cretaceous. 
Middle  Cretaceous. 
Lower  Cretaceous. 


Wealdea. 

Oolite. 

Lias. 


Keuper. 

Muschelkalk. 

Bunter-sandstein. 


In  the  preceding  sections,  Archwan  is  at  the  bottom,  on  the 
left ;  above  it  there  are  the  names  Silurian,  Devonian,  and  so 
on ;  and  the  names  of  the  Periods,  Primordial,  Canadian, 
Trenton,  etc.,  dividing  off  these  Ages,  on  the  right. 

The  names  of  the  Periods  in  the  first  part  of  the  section 
(those  of  the  Paleozoic),  the  first  excepted,  are  derived  from 
the  names  of  American  rocks  or  localities.  The  names  on 
the  other  part  are  mostly  European,  as  the  series  of  rocks  it 
contains  (those  of  Mesozoic  and  Cenozoic  time)  are  more  com- 
plete in  Europe  than  in  America. 


SUBDIVISIONS  IN   THE  HISTORY, 


195 


196  HISTORICAL  GEOLOGY. 

The  various  strata  in  the  formations  of  an  age  are  very 
diversified  in  character,  limestones  being  overlaid  abruptly 
by  sandstones,  conglomerates,  or  shales,  or  either  of  these 
last  by  limestones ;  and  each  may  be  very  different  from  the 
following  in  its  fossils.  These  abrupt  transitions  in  the 
strata  are  proofs  that  there  were  great  changes  at  times  in 
the  conditions  of  the  region  where  the  strata  were  formed, 
and  the  transitions  in  the  kinds  of  fossils  are  evidence  of 
great  destructions  at  intervals  in  the  life  of  the  seas.  Such 
transitions,  therefore,  naturally  divide  off  the  ages  into 
smaller  portions  of  time,  or  periods,  as  they  are  called.  By 
transitions  similar  in  kind,  but  not  so  great,  periods  may 
often  be  subdivided  into  still  smaller  parts,  or  epochs. 

The  map  on  page  195  represents  the  distribution  of  the  rocks 
of  the  different  ages,  as  surface-rocks,  over  the  United  States 
and  Canada.  The  areas  indicated  by  the  different  kinds  of 
lining  are  stated  on  the  map. 

The  areas  left  white  are  of  unascertained  or  doubtful  age ; 
cr.  marks  outcrops  of  Cretaceous  on  the  Atlantic  border ; 
C.,  Cincinnati ;  CL,  Claiborne ;  V.,  Vicksburg. 

The  Silurian  strata  may  underlie  the  Devonian,  end  both 
Silurian  and  Devonian  the  Carboniferous.  The  black  areas 
of  the  Carboniferous  period  do  not,  therefore,  indicate  the 
absence  of  Devonian  and  Silurian,  but  only  that  the  Car- 
boniferous strata  are  the  surface  strata  over  the  region. 
There  may  even  be  exceptions  to  this  remark  with  regard 
to  the  surface  strata  ;  for,  over  the  areas  thus  marked  Car- 
boniferous, older  rocks  may  occur  in  some  of  the  bluffs  along 
the  valleys,  or  occupy  small  areas  in  the  region,  which  are 
too  limited  to  be  noted  on  so  small  a  map. 

The  map  on  page  197  represents  the  surface-rocks  of  the 
State  of  New  York  and  Canada,  the  several  areas  corre- 
sponding to  the  periods.  For  the  Silurian,  the  lines  or  dots 
are  drawn  horizontally,  as  in  the  preceding,  and  for  the  De- 
vonian, vertically.  There  is  no  Carboniferous,  except  near 
the  southern  border  of  the  State  of  New  York. 


SUBDIVISIONS   IN  THE   HISTORY. 


197 


Geological  Map  of  New  Yorlr  and  Canada. 


198 


ARCHAEAN  TIME. 


No.  1.  The  Archseaii. 

2.  The  Primordial  Period. 

3.  The  Canadian  Period. 

4.  The  Trenton  Period. 

5.  The  Niagara  Period. 

6.  The  Salina  Period. 

9.  The  Upper  Helderberg  Period. 

10.  The  Hamilton  Period. 

11.  The  Chemung  Period. 

12.  The  Catskill  Period. 

Fig.  187. 


~ 


Lower 
Silurian. 

Upper 
Silurian. 


Djvouian. 


Carbonif-  Devonian, 

erous. 


Silurian. 


In  the  section  in  Fig.  187,  the  rocks  of  the  successive 
periods  are  represented  in  order,  from  the  Archaean,  in  North- 
ern New  York,  southwestward  to  the  Coal-formation  of  Penn- 
sylvania, showing  that  they  succeed  one  another  on  the  map 
simply  because  they  come  to  the  surface  in  succession.  The 
amount  of  dip  and  its  regularity  are  greatly  exaggerated  in 
the  section  ;  and  there  is  no  attempt  to  give  the  relative 
thickness  of  the  beds. 


GEOGRAPHICAL  DISTRIBUTION. 


199 


L— ARCHAEAN   TIME. 
1.    Rocks:  Kinds  and  Distribution. 

1,  Distribution.  —  The  Archaean  era  commenced  with  the 
origin  of  the  earth's  crust,  arid  includes  the  oldest  rocks  of 
the  globe.  Its  formations  are  those  upon  which  the  fos- 
siliferous  rocks  of  the  Silurian  and  subsequent  ages  have 
been  spread  out,  and  the  material  out  of  which  most  of 
these  later  rocks  have  been  made. 

The  Archaean  rocks  extend  around  the  whole  sphere ;  but, 

Fig.  188. 


Archaean  Map  of  North  America. 


in  general,  they  are  concealed  from  view  by  subsequent  for- 
mations. In  North  America  they  are  surface  rocks  over  a 
krge  area  north  of  the  great  lakes,  shaped  like  the  letter  V, 


200  ARCII^AN  TIME. 

the  longer  branch  of  which  area  runs  northwest  to  tlio  Arctic 
Ocean,  and  the  shorter,  northeast  to  Labrador.  The  white 
area  on  the  preceding  map,  in  what  is  now  British  America, 
is  the  portion  of  the  continent  here  referred  to.  There  is 
also  a  small  Archaean  area  in  Northern  New  York  (see  map 
page  197);  the  Highlands  of  Putnam  County,  New  York,  and 
of  New  Jersey  is  Archaean,  and  so  also  in  part  the  Blue 
Pudge  of  Virginia;  another  south  of  Lake  Superior;  and  a 
fjv/  other  spots  east  of  the  Rocky  Mountains.  Some  high 
ranges  also  of  the  Rocky  Mountain  region  are  Archaean. 

In  Europe  Archaean  rocks  are  in  view  in  the  great  iron  re- 
gions of  Sweden  and  Norway,  in  Bohemia,  and  in  Scotland. 

2.  Kinds  of  Rocks.  —  The  rocks  are  mostly  crystalline  rocks, 
such   as   granite,    syenyte,    gneiss,    syenytic     gneiss,     mica 
schist,  hornblende  schist,  chlorite  slate,  and  granular  lime- 
stone.    But  besides  these  there  are  some  hard  conglomerates, 
quartz-rocks  or  gritty  sandstones,  and  slates.     The  beautiful 
iridescent  feldspar  called  labradorite  (page  22)  is  a  common 
constituent  of  some  of  the  coarse  crystalline  or  granitic  rocks. 

An  abundance  of  iron  is  one  characteristic  of  the  beds. 
The  rocks  very  often   contain   hornblende,  an   iron-bearing 
mineral,  or  black  mica,  also  iron-bearing.     Along  with  the 
rocks  there  are,  in  some  regions,  immense  beds  of  iron  ore 
(i  i  i,  in  Fig.  189).     In  Northern  New 
Pig.  189.  York  the  beds  are  100  to  200  feet  thick. 

Similar  iron-ore  beds  occur  in  New  Jer- 
sey, Michigan,  south  of  Lake  Superior, 
and  in  Missouri.  Graphite  is  common 
in  some  places,  and  constitutes  2  to  30 
per  cent  of  some  beds,  especially  of  the  limestones. 

3.  Disturbance  and  Crystallisation  of  the  Rocks. — The  layers 
of  gneiss  and  other  schistose  rocks,  with  the  included  lime- 
stones, are   nowhere  horizontal ;   but,  instead  of  this,  they 
dip  at  all  angles,  and  are  often  flexed  or  folded  in  a  most 
complex  manner.     Fig.  190  represents  the  folded  character 
of  the  Archasan  rocks  of  Canada.     The  folded  rocks  in  this 


ORIGIN   OF   THE   ROCKS.  201 

figure  are  overlaid  by  beds  that  are  nearly  horizontal,  which 
belong  to  the  Lower  Silurian. 

Owing  to  the  discolations  and  uplifts  which  the  rocks  have 
undergone,  the  iron-ore  beds  look  like  veins ;  and  even  the 
strata  of  crystalline  limestone  have  often  a  similar  vein-like 

Fig.  190. 
2 


Fig.  190,  by  Logan,  from  the  south  side  of  the  St.  Lawrence  in  Canada,  between  Cascade 
Point  and  St.  Louis  Rapids  ;  1,  Archaean  gneiss;  2,  2,  Silurian  strata. 

appearance.  Where  strata  have  been  thrown  up  so  that  the 
layers  stand  vertical,  the  included  bed  of  ore  will  be  vertical 
also,  and  will  descend  downward  in  the  same  manner  as  a 
true  metallic  vein ;  and  through  the  breaking  and  faulting  of 
the  strata  many  of  those  irregularities  would  result  that  are 
so  common  in  veins. 

Gneiss,  mica  schist,  granular  limestone,  and  other  crystal- 
line rocks  have  been  described  on  page  35  as  metamorphic 
rocks,  —  rocks  that  were  once  horizontal  sandstones,  shales, 
and  stratified  limestones,  and  which  have  been,  by  some  pro- 
cess, crystallized.  The  gneiss  and  schists  in  Archaean  regions, 
although  upturned  at  all  angles,  are  actually  in  layers  or 
strata  alternating  with  one  another,  as  common  with  ordinary 
sandstones  and  shales ;  and  the  ore-beds  are  conformable  to 
the  layers  of  schist  and  quartzyte  in  which  they  occur. 

4.  Conclusions  as  to  the  Origin  of  the  Rocks. —  The  following 
conclusions  hence  follow :  1.  That  the  Archasan  rocks  here 
referred  to  were  originally  horizontal  strata  of  sandstones, 
shales,  and  limestones;  2.  That  after  their  formation  they 
were  pushed  out  of  place  by  some  great  movement  of  the 
earth's  crust,  which  uplifted  and  folded  them,  so  that  now 
they  are  nowhere  horizontal;  3.  That,  besides  being  dis- 
placed, they  were  also  crystallized,  —  that  is,  changed  into 
metamorpliic  rocks. 

The  thickness  of  the  Archaean  rocks  of  Canada  is  stated  to 
exceed  30,000  feet.  So  great  an  accumulation  of  marine  beds 
is  proof  that  the  era  was  very  long. 


202  ARCHAEAN  TIME. 

It  is  altogether  probable  that  the  time  of  the  uplifting  and 
that  of  the  metamorphism  were  the  same.  There  may  have 
been  many  such  metamorphic  epochs  in  the  course  of  Archaean 
time.  But,  since  even  the  latest  beds  of  the  Archaean  are  thus 
upturned  and  crystallized,  an  extensive  revolution  of  this  kind 
must  have  been  a  closing  event  of  the  age.  Fig.  190  shows 
that  the  upturning  preceded  the  formation  of  the  lowest  Silu- 
rian beds,  for  these  lie  undisturbed  over  the  folded  and  crys 
tallized  Archaean. 

Below  the  surface  Archaean  rocks  there  must  be  others, 
constituting  the  interior  portions  of  the  earth's  crust.  If  the 
earth  were  originally  a  melted  globe,  as  appears  altogether 
probable,  the  earth's  crust  is  its  cooled  exterior.  Whenever 
the  crust  formed,  its  surface  must  have  been  at  once  worn  by 
the  waves,  wherever  within  their  reach,  and  deposits  of  sand, 
pebbles,  and  clay  must  have  been  formed;  and  in  this  way 
the  Archaean  formations  were  begun.  But  at  the  same  time 
that  these  surface  strata  were  in  progress,  the  crust  would 
have  been  increasing  in  thickness  within  by  the  cooling 
which  was  continuing  its  progress.  Of  the  interior  rock  of 
the  crust  little  is  known. 

2.  Life. 

The  Archaean  rocks  contain  no  distinct  fossil-plants.  If 
plants  existed  then,  they  were  Sea-weeds;  for  remains  of 
none  higher  than  sea-weeds  occur  in  the  overlying  Lower 
Silurian  formations.  It  is  possible  that  Lichens  existed  over 
the  exposed  rocks ;  for  such  plants  away  from  waters  would 
not  have  left  their  remains  in  the  mud  or  sands  of  the  seas. 
There  may  also  have  been  Fungi  of  simple  kinds.  But  there 
is  reason  to  believe  that  Mosses  and  higher  plants  were  all 
absent,  for  none  of  these  have  been  found  in  any  Lower 
Silurian  strata. 

The  graphite,  abundant  in  some  beds  in  Canada,  is  probable 
evidence  of  the  existence  of  plants,  because  it  is  known  that 


GENERAL  OBSERVATIONS. 


203 


Fig.  191. 


in  later  times  graphite  has  been  formed  out  of  their  remains. 
The  limestone  beds  suggest  the  idea  that  there  was  present 
either  vegetable  or  animal  life ;  for  almost  all  limestones  (see 
page  63)  are  of  organic  origin. 

The  annexed  figure  represents 
what  has  been  regarded  as  a  fossil 
form,  and  named  Eozoon  Cana- 
dense.  It  is  supposed  to  have 
been  a  coral-like  mass  made  by 
Protozoans  of  the  class  of  Khizo- 
pods,  the  simplest  of  all  kinds 
of  animal  life.  Each  dark  layer 
in  the  mass  is  supposed  to  mark 
the  position  of  the  animals.  Its 
animal  nature  has  not,  however, 
been  placed  beyond  doubt.  Still, 
it  is  altogether  probable  that 
Ehizopods  existed  in  the  waters  Eozoou  Canadense. 

before  the  close  of  the  Archaean 

era,  and  that  the  beds  of  limestone  have  been  made  of 
their  minute  shells,  or  else  of  calcareous  Nullipores. 


3.  General  Observations. 

The  large  Archaean  area  on  the  map,  page  199,  represents 
the  main  portion  of  the  dry  land  of  North  America  in  the 
later  part,  or  at  the  close,  of  the  Archaean  age ;  for  it  consists 
of  the  rocks  made  during  the  age,  and  is  bordered  on  its  dif- 
ferent sides  by  the  earliest  rocks  of  the  next  age.  It  is  the 
outline,  approximately,  of  Archaean  North  America,  or  the 
continent  as  it  appeared  when  the  Silurian  age  opened.  It 
is,  therefore,  the  beginning  of  the  dry  land  of  North  America, 
the  original  nucleus  of  the  continent.  The  smaller  Archaean 
areas  mentioned  appear  to  have  been  mountain  ridges  and 
islands  in  the  great  continental  seas. 

Europe  had  its  Archaean  lands  at  the  same  time  in  Scandi- 


204  PALEOZOIC  TIME. 

navia,  Scotland,  Bohemia,  and  some  other  points ;  and  prob- 
ably each  of  the  other  continents  was  then  represented  by  its 
spot,  or  spots,  of  dry  land.  All  the  rest  of  the  sphere,  except- 
ing these  limited  areas,  was  an  expanse  of  waters. 

The  facts  to  be  presented  under  the  Silurian  age  teach  that 
the  great  but  yet  unmade  continents,  although  so  small  in  the 
amount  of  dry  land,  were  not  covered  by  the  deep  ocean,  but 
only  by  comparatively  shallow  oceanic  waters.  They  lay  just 
beneath  the  waves,  already  outlined,  prepared  to  commence 
that  series  of  formations  —  the  Silurian,  Devonian,  Carbonif- 
erous, and  others  —  which  was  required  to  finish  the  crust  for 
its  ultimate  continental  purposes.  Portions  may  have  been 
at  times  a  few  thousands  of  feet  under  water,  but  in  general 
the  depth  was  small  compared  with  that  of  the  ocean. 

We  thus  gather  some  hints  with  regard  to  the  geography 
of  America  in  the  period  of  its  first  beginnings. 

The  outlines  of  the  Northern  Archaean  area  on  the  map, 
page  199 — the  embryo  of  the  continent  —  and  the  directions 
of  the  other  Archaean  lands  are  very  nearly  parallel  to  the 
coast  lines  of  the  present  continent.  The  Archasan  lands, 
both  in  North  America  and  Europe,  are  largest  in  the  more 
northern  latitudes. 


II.  —  PALEOZOIC    TIME. 

PALEOZOIC  TIME  includes  three  ages  :  — 

1.  The  Age  of  Invertebrates,  or  Silurian  Age. 

2.  The  Age  of  Pishes,  or  Devonian  Age. 

3.  The  Age  of  Coal-Plants,  or  Carboniferous  Age. 

In  describing  the  rocks  of  these  ages  over  North  America, 
and  the  events  connected  with  their  history,  there  are  four 
distinct  regions  to  be  noted,  —  distinct,  because  in  an  impor- 
tant degree  independent  in  their  history.  These  are,  — 

1,  The  Eastern  border  region,  or  that  near  the  Atlantic  bor- 
der, including  Central  and  Eastern  New  England,  New  Bruns- 


SILURIAN  AGE.  205 

wick  and  Nova  Scotia,  and  the  coast  region  south  of  New 
York. 

2.  The  Appalachian  region,  or  that  now  occupied  by  the 
Appalachian  Mountain  chain,  from  Labrador  on  the  north, 
along  by  the  Green  Mountains,  and  the  continuation  of  the 
heights  through  New  Jersey,  Pennsylvania,  Virginia,  East- 
ern Tennessee,  and  so  south  westward  to  Alabama. 

3.  The  Interior  Continental  region,  or  that  west  of  the  Appa- 
lachian region,  continued  over  much  of  the  present  eastern 
slope  of  the  Rocky  Mountain  chain. 

4.  The  Western  border  and  Rocky  Mountain  region,  from  the 
crest  of  the  Rocky  Mountains  west  ,vard. 

I.    AGE    OF   INVERTEBRATES,  or  SILURIAN   AGE. 

This  Age  is  called  Silurian  from  the  region  of  the  ancient 
Silures  in  Wales,  where  the  rocks  occur.  It  was  first  so 
named  by  Murchison. 

The  Age  is  naturally  divided  into  Lower  and  Upper  Silurian, 
each  corresponding,  in  America,  to  three  periods,  thus  :  — 

1.  Lower  Silurian. 

'1.  Primordial,  or  Cambrian  Period :  including  the  Cam- 
brian of  England,  with  the  Lingula  flags. 

2.  Canadian  Period:   including  the  Tremadoc  slates,  the 
Skiddaw  slates,  and  Stiper-stones  group  of  Great  Britain. 

3.  Trenton   Period :    including   the    Llandeilo   flags,    Bala 
limestone,  and  Caradoc  sandstone  of  Great  Britain. 

2.  Upper  Silurian. 

1.  Niagara  Period:   including  the  Wenlock  beds  of  Great 
Britain,  with  the  Upper  Llandovery. 

2.  Salina  Period. 

3.  Lower  Helderbcrg  Period  :  including  part  of  the  Ludlow 
beds  of  Great  Britain. 

4.  Oriskany  Period :  including  the  upper  part  of  the  Lud- 
low beds. 


206  PALEOZOIC   TIME.  — LOWER   SILURIAN. 

1.   Primordial  Period. 
I.    Rocks:   Kinds  and  Distribution. 

The  strata  of  the  Primordial  period,  in  America,  over  the 
Interior  Continental  basin,  are  exposed  to  view  at  intervals 
from  New  York  to  the  Mississippi  River ;  beyond  the  river, 
over  some  parts  of  the  eastern  and  western  slopes  of  the 
Rocky  Mountains ;  and  also  in  Texas.  The  area  on  the  map 
of  New  York  and  Canada  (page  197)  is  that  numbered  2,  lying 
next  to  the  Archsean.  There  is  reason  to  believe,  from  the 
many  points  at  which  the  strata  come  to  the  surface,  that 
they  extend  over  the  larger  part  of  the  continent  outside  of 
the  Archaean  area  represented  on  the  map,  page  199  though 
concealed  by  other  less  ancient  strata  over  most  of  the  sur- 
face. 

Through  the  Interior  region  the  lower  rocks  are  in  part  a 
sandstone,  —  called  the  Potsdam  sandstone,  from  a  locality  in 
Northern  New  York.  The  sandstone  beds  contain,  in  many 
places,  ripple-marks  (Fig.  24,  page  46) ;  mud-cracks  (Fig.  26) ; 
layers  showing  the  wind-drift  and  ebb-ancl-flow  structure 
(Figs.  22  /,  e)  ;  worm-burrows,  and  also  occasionally  the 
tracks  of  some  of  the  animals  of  the  period. 

In  the  Appalachian  region  in  Vermont,  north  in  Canada, 
and  in  Pennsylvania,  etc.,  the  rocks  are  slates  overlying 
sandstone,  along  with  some  limestone,  the  whole  2,000  to 
7,000  feet  or  more  thick. 

In  the  Eastern  border  region  beds  of  the  period  occur  at 
Braintree,  near  Boston,  at  St.  John's,  New  Brunswick,  and 
on  the  Labrador  coast.  These  are  the  oldest  of  American 
Primordial  rocks,  and  have  been  distinctively  called  the 
Acadian  group. 

In  Great  Britain  the  Primordial  rocks  are  hard  sandstones 
and  slates.  The  uppermost  include  the  Lingula  flags.  They 
are  most  extensively  in  view  in  North  arid  South  Wales  and 
in  Shropshire.  The  lower  portion  of  the  series,  of  great  thick- 


PRIMORDIAL  PERIOD.  207 

ness,  consisting  of  slates  and  other  rocks,  was  named  Cam- 
brian by  Sedgwick 

In  Lapland,  Norway,  Sweden,  and  Bohemia,  Primordial 
strata  have  been  observed.  If  the  strata  of  later  date  could 
be  removed  from  the  continents,  we  should  probably  find  the 
Primordial  beds  extensively  distributed  over  all  the  conti- 
nents. 

2.    Life. 

These  most  ancient  of  fossiliferous  rocks  contain  no  re- 
mains of  terrestrial  life.  The  plants  of  the  period  that  left 
traces  in  the  rocks  were  all  Sea-weeds.  Among  animals,  the 
sub-kingdoms  of  Radiates,  Mollusks,  and  Articulates  were  rep- 
resented by  water-species,  and  by  these  only ;  there  is  no  evi- 
dence that  there  were  any  Vertebrates. 

The   older  sandstone  abounds  in  many  places  in  a  shell 
smaller,  in  general,  than  a  finger-nail,  related  to  the   Fig  192 
modern  Lingula  (Fig.   192).      It  is  the  shell  of  a 
Mollusk  of  the  tribe  of  Brachiopods.     It  stood  on 
a  stem,  when  alive,  as  represented  in  Fig.  157,  page 
181.     These  shells  are  so  characteristic  of  the  beds 

i  L     -i    j.1  prima. 

in  many  regions  as  to  have  suggested  the  name 
Lingula  flags,  or  Lingula  sandstone.     Among  Mollusks  there 
were  only  Brachiopods  for  the  greater  part  of  the  Primordial 
period ;  but  in  the  later  division  appear  some  species  of  La- 
mellibranchs,  Pteropods,  Gasteropods,  and  Cephalopods. 

Another  tribe  very  prominent  among  the  earliest  of  the 
earth's  animals  is  that  of  Trilobites,  of  the  sub-kingdom  of 
Articulates,  and  class  of  Crustaceans. 

One  of  the  largest  of  them,  and  a  kind  characteristic  of  the 
Lower  or  Acadian  division  of  the  Primordial,  is  represented 
in  Fig.  193,  one  sixth  the  natural  size.  Its  total  length,  when 
living,  must  have  been  eighteen  inches  or  more,  arid  hence  it 
was  about  as  large  as  any  living  Crustacean.  The  specimen 
figured  was  found  at  Brnintree,  south  of  Boston.  As  shown, 
it  had  large  eyes  situated  on  the  head-shield,  —  evidence. 


208 


PALEOZOIC   TIME.  — LOWP;R   SILURIAN. 


Fi-?.  193. 


like  other  points  in  the  structure  that  the  species,  although  of 

the  earlier  division  of  the  Primordial,  were  far  removed  from 

simple  germ-like  forms.  Tri- 
lobites  are  supposed  to  have 
had  membranous  or  foliaceous 
plates  for  swimming.  Fig.  194 
shows  the  track  of  a  large 
animal  (reduced  to  one  sixth) 
found  by  Logan  in  the  Canada 
beds,  which  may  have  been 
made  by  one  of  the  great  Trilo- 
bites  as  it  crawled  over  the  sand. 
The  existence  of  marine  worms 
among  the  earliest  animals  of 
the  globe  is  proved  by  the 
great  numbers  of  worm- holes 
or  burrows  in  the  sandstones, 
now  filled  with  hard  sandstone 
like  that  of  the  rock.  They 
are  very  similar  to  the  holes 
made  by  such  worms  in  the 
sands  of  sea-shores  at  the  pres- 
ent time.  One  species  has  been 
called 

Scolithus  linearis.    These  worm-holes 

are    common   in    the   European   as 

well  as  American  Primordial  sand- 
stones. 

There  were  also   Crinoids  of  the 

sub-kingdom  of  Eadiates  (page  65), 

for    disks   from    the   broken   stems 

of    Crinoids    are    not    uncommon. 

And  among  Protozoans  there  were 

Sponges,   and   probably  the  minute 

Ehizopods  (page  66). 

Sponges    among    Protozoans,    Crinoids    among    Eadiates, 


THILOBITE.  —  Paradoxidea  Harlani 
(x  4). 


Fig.  194. 


Track  of  a  Trilobite  (X  |). 


PRIMORDIAL  PERIOD.  209> 

Brachiopods  and  some  representatives  of  other  tribes  among 
Mollusks,  Worms  and  Trilobites  among  Articulates,  and  Sea- 
weeds among  Plants,  make  up  the  living  species  thus  far  dis- 
covered; and  iii  this  Primordial  population,  Trilobites  took 
the  lead.  There  is  as  yet  no  evidence  that  the  dry  Primor- 
dial hills  bore  a  Moss  or  Lycopod,  or  harbored  the  meanest 
Insect,  or  that  the  oceans  contained  a  single  Fish. 

3.   General  Observations. 

The  ripple-marks,  mud-cracks,  and  tracks  of  animals  pre- 
served in  this  most  ancient  of  Paleozoic  rocks  are  records 
left  by  the  waves,  the  sun,  and  the  life  of  the  period,  as  to 
the  extent  and  condition  of  the  continent  in  that  early  era. 
These  markings  teach  that  when  the  beds  were  in  progress 
a  large  part  of  the  continent  lay  at  shallow  depths  in  the 
sea,  so  shallow  that  the  waves  could  ripple  its  sands ;  that 
over  other  portions  the  surface  was  a  sand-flat  exposed  at 
low  tide  ;  or  a  sea-beach,  the  burrowing-place  of  worms  • 
or  a  mud-flat,  that  could  be  dried  and  cracked  under  the 
heat  of  the  sun,  or  in  a  drying  atmosphere. 

With  such  evidences  of  shallow  water  or  emerged  flats 
in  a  formation  extending  widely  over  the  continent,  it  is  a 
safe  conclusion  that  the  North  American  continent  was 
at  the  time  in  actual  existence,  and  probably  not  far  from 
its  present  extent ;  and,  although  partly  below  the  sea-level, 
and  in  some  places  deeply  so,  it  was  generally  at  shallow 
depths.  The  same  may  prove  to  have  been  true  of  the  other 
continents.  There  is,  in  fact,  evidence  of  other  kinds  which, 
taken  in  connection  with  the  above,  leaves  little  doubt  that 
the  existing  places  of  the  deep  ocean  and  of  the  continents 
were  determined  even  in  the  first  formation  of  the  earth's 
crust  in  the  early  Archaean  era,  and  that,  in  all  the  move- 
ments that  have  since  occurred,  the  oceans  and  continents 
have  never  changed  places. 

This  preservation  of  markings,  seemingly  so  perishable,  on 
the  early  shifting  sands,  is  a  very  instructive  fact.  They 

14 


210  PALEOZOIC   TIME.  — LOWER  SILUKIAN. 

illustrate  part  of  the  means  by  which  the  earth  has,  through 
time,  been  recording  its  own  history.  The  track  of  a  Trilo- 
bite,  or  of  a  wavelet,  is  a  mould,  in  sand  or  earth,  into  which 
other  sands  are  cast  both  to  copy  and  preserve  it ;  for  if  the 
waves  or  currents  that  succeed  are  light,  they  simply  spread 
new  sands  over  the  indented  surface,  without  obliterating 
the  mould ;  and  so  the  addition  of  successive  layers  only 
buries  the  markings  more  deeply  and  thus  protects  them 
against  destruction.  When,  finally,  consolidation  takes 
place,  the  track  or  ripple-mark  is  made  as  enduring  as 
the  rock  itself. 

After  the  formation  in  North  America  of  the  great  Primor- 
dial sandstone,  there  was  a  change  in  the  condition  of  the 
surface,  especially  over  the  interior  of  the  continent.  For 
limestone  strata  began  then  to  form  where  sandstones  were 
in  progress  before.  This  change  was  probably  some  increase 
in  the  depth  and  clearness  of  the  Interior  Continental  sea. 
Along  the  borders  of  this  sea  —  that  is,  in  New  York  and 
along  the  Appalachian  region  from  Quebec  into  Virginia  — 
the  rock  was  a  sandstone  or  shale,  with  some  subordinate 
strata  of  limestone. 

2.    Canadian  and  Trenton  Periods. 

The  CANADIAN  period  is  so  named  from  Canada,  where 
the  rocks  are  well  displayed  and  have  been  most  thoroughly 
studied;  and  the  TRENTON  period,  from  Trenton  Falls,  just 
north  of  Utica,  the  river  at  the  Falls  running  between 
high  bluffs  of  Trenton  limestone. 

In  Great  Britain  the  first  of  these  periods  covers  the  era 
01  the  Tremadoc  and  Skiddaw  slates,  and  the  latter  that  of 
the  Bala  limestone  and  Llandeilo  flags. 

I.    Rocks:   Kinds  and  Distribution. 

In  the  Primordial  period  the  rock  deposits  formed  over  the 
North  American  continent  were  mainly  of  sands  or  mud, 


CANADIAN  AND  TRENTON  PERIODS.  211 

making  sandstones  and  shales ;  and  but  little  limestone  was 
formed.  The  Canadian  period  is  one  of  transition  to  a  third, 
the  Trenton,  when  limestones  were  in  progress  over  nearly 
the  whole  breadth  of  the  continent,  the  Appalachian  and 
Arctic  regions,  as  well  as  the  Interior  Continental. 

The  rocks  of  the  Canadian  period  to  the  eastward  in  New 
York  and  Canada  are,  —  1.  A  sandstone  associated  in  places 
with  much  limestone,  and  called,  in  allusion  to  the  limestone, 
the  Calciferous  sand-rock ;  2.  South  of  Quebec,  shale,  sand- 
stone, and  thin  beds  of  limestone,  called  the  Quebec  group ; 
3.  A  limestone  formation,  called  the  Chazy  limestone,  from  a 
place  of  that  name  in  Northern  New  York.  The  latter  lime- 
stone (with  probably  beds  of  the  Quebec  group)  makes  part 
of  the  granular  limestone  or  marble  of  the  Green  Mountains 
from  Vermont  to  Connecticut,  and  has  great  thickness  also  in 
Pennsylvania  and  Virginia.  In  the  Interior  basin  the  rock 
of  the  period  is  mainly  limestone  —  in  Iowa  and  Wisconsin 
the  Lower  Magnesian  limestone  —  excepting  to  the  north, 
where  the  upper  part  is  sandstone  (St.  Peter's  sandstone)  and 
along  the  south  side  of  Lake  Superior,  where  there  is  only 
sandstone.  The  "  Pictured  Kocks  "  and  the  thick  sandstones 
of  Keweenaw  Point,  remarkable  for  their  intersection  by  trap 
dikes  and  veins  of  copper,  have  been  supposed  to  be  of  this 
period,  but  are  probably  Primordial. 

The  Trenton  period  is  remarkable  for  its  extensive  lime- 
stone formation.  The  limestone  occurs  in  Canada ;  in  New 
York  (the  beds  at  Trenton  Falls  giving  it  its  name) ;  along  the 
Appalachian  range ;  in  Ohio  and  other  States  of  the  Ohio  and 
Mississippi  basin  ;  from  Wisconsin,  northwestward  along  the 
west  side  of  the  Archaean  area ;  and  in  the  Arctic  regions.  It 
is  in  most  places  Mil  of  fossils.  The  "  Birdseye  "  and  "  Black 
Eiver"  limestones  are  part  of  the  Trenton  formation.  The 
rock  of  the  later  part  of  the  Trenton  period  (called  the  Cincin- 
nati epoch),  in  New  York,  and  the  Appalachians,  is  shale  and 
sandstone,  and  even  in  the  Interior  basin  the  limestones  are 
often,  as  about  Cincinnati,  quite  clayey  or  impure.  The  Utica 


212  PALEOZOIC  TIME.— LOWER  SILURIAN. 

shale  and  Lorraine  shale  belong  to  this  era.  The  crystalline 
limestone  (marble)  of  Vermont  and  Western  Massachusetts 
and  Connecticut,  with  the  associated  hydromica  slate,  clay- 
slate,  mica  schist,  and  quartzyte,  is  Lower  Silurian ;  it  con- 
tains, at  several  localities  in  Vermont,  Canadian  and  Tren- 
ton fossils. 

The  thickness  of  the  rocks  of  the  Canadian  and  Trenton 
periods  in  Pennsylvania  is  over  7,500  feet ;  while  in  Illinois 
it  is  but  750  feet,  and  in  Missouri  about  2,000  feet. 

The  rocks  of  this  era  in  Great  Britain  are  shales  and  shaly 
sandstones,  with  but  little  limestone.  The  Tremadoc  slates 
are  dark  slates  over  1,000  feet  thick  in  Wales,  passing  below 
into  the  Lingula  flags,  and  above  into  the  Llandeilo  beds.  The 
Llandeilo  flags  are  shaly  sandstones ;  and,  together  with  the 
associated  shales,  they  have  a  thickness  of  many  thousand 
feet.  Above  them  there  are  the  Caradoc  sandstone  of  Shrop- 
shire, and  the  Bala  formation,  the  latter  sandy  slates  and  sand- 
stone, with  thin  beds  of  limestone,  in  Wales.  In  Scandinavia 
the  rocks  are  limestone,  overlaid  by  slates  and  flags ;  and  in 
the  Baltic  provinces  of  Eussia  —  part  of  the  Interior  Conti- 
nental portion  of  the  Eastern  Continent  —  they  are  mainly 
limestones. 

2.    Life. 

The  life  of  these  periods,  like  that  of  the  Primordial,  was, 
as  far  as  evidence  has  been  collected  from  the  American  or 
foreign  rocks,  marine,  plants  excepted. 

The  plants  found  fossil  are  Sea-weeds,  and  also  the  first  of 
land  plants,  of  the  tribes  of  Lycopods  and  Ferns. 

All  the  sub-kingdoms  of  animals  were  represented,  with  the 
exception  of  the  Vertebrates.  Among  Radiates  there  were 
Corals  and  Crinoids ;  among  Mollusks,  representatives  of  all 
the  several  orders ;  among  Articulates,  the  water-divisions, 
Worms  and  Crustaceans. 

1.  Radiates.  —  The  Canadian  beds,  especially  the  finer 
slates  and  shales,  are  remarkable  for  the  great  abundance 


CANADIAN   AND   TRENTON   PERIODS. 


213 


of  very  delicate  plume-like  remains  of  Kadiate  life,  called 
Graptolites,  from  the  Greek  7pac/>o>,  /  write. 


GRAPTOLITES.  —  Fig.  195,  Dichograptus  Logani,  the  central  portion  of  a  radiating  group 
of  stems  with  parts  of  the  stems  ;  196',  same,  portion  of  one  of  the  stems,  and  196  a,  part 
of  stems  enlarged  ;  197,  Uiplojraptus  pristis  ;  198,  19J,  Pnyilograptus  typus ;  200,  the 
young  of  a  Graptolite. 

A  few  of  the  kinds  are  represented  in  Figs.  195,  196,  198- 
200,  and  one  spacies,  from  the  later  part  of  the  Trenton 
period,  in  Fig.  197.  In  the  living  state  there  were  cells 
along  the  notched  margin,  one  for  each  notch,  from  which 
little  star-shaped  animals  extruded  themselves.  They  be- 
long to  the  tribe  of  Hydroids,  under  Acalephs,  described 
on  page  184. 

Fig.  201  represents  one  of  the  Corals  of  the  Trenton.  Its 
shape  is  that  of  a  curved  cone,  a  little  like  a  short  horn,  the 
small  end  being  the  lower.  At  top,  when  perfect,  the  cavity 
of  the  coral  is  divided  off  by  plates  radiating  from  the  centre. 
Such  corals  are  called  Cyatlwphijlloid  corals,  from  the  Greek 
/cva9os,  cup,  and  c])v\\ov,  leaf,  alluding  to  the  cup  full  of  radi- 
ating leaves  or  plates.  When  living,  the  coral  occupied  the 
interior  of  an  animal  similar  to  that  represented  in  Fig.  168, 
or  Fig.  169  on  page  183. 

Another  kind  of  coral,  of  a  hemispherical  form,  and  made 
up  of  very  fine  columns,  is  represented  in  Figs.  202,  203,  the 
latter  showing  the  interior  appearance.  It  is  called  Chcctetes 
lycoperdon.  Another,  of  coarser  columns,  —  each  nearly  a 
sixth  of  an  inch  in  diameter, — is  called  the  Columnaria  alveo- 


214 


PALEOZOIC   TIME.  —  SILURIAN. 


lata.  In  a  transverse  section  the  columns  are  divided  off  by 
horizontal  partitions.  Masses  of  this  coral  have  been  found 
that  weigh  each  between  two  and  three  thousand  pounds. 

Fig.  204  shows  the  form  of  one  of  the  Crinoids,  though  the 
stem  on  which  it  stood  is  mostly  wanting,  and  the  arms  are 
not  entire.  The  mouth  was  in  the  centre  above,  and  the  ani- 
mal was  related  to  the  Comatula  among  star-fishes,  from 
which  it  differed  in  being  attached  to  the  sea-bottom  by  means 
of  a  jointed  stem.  There  were  also  true  star-fishes  in  the  seas. 


Figs.  201-212. 

204 


202 


RADIATES  OF  THE  TRENTON  PERIOD  -  Fig.  201,  Petraia  corniculum  ;  202,  203, 
Chsetetes  lycoperdon;  204,  Lecanocrinus  elegans.  —  MOLLTJSKS  :  Fig.  205,  Stictopora 
acuta ;  206,  Orthis  testudinaria ;  207,  Orthis  occidentalis  :  208,  Leptsena  sericea  ;  209 
Ambonychia  bellistriata  ;  210,  Raphistoma  lenticularis  ;  211,  Orthoceras  junceum.  — 
ARTICULATES  :  Fig.  212,  Asaphus  gigas.  ^ 

2.  Mollusks.  —  Among  Mollnsks  Bryozoans  were  very  com- 
mon :  the  fossils  are  small  cellular  corals  :  one  is  shown  in 
Fig.  205.  Brachiopods  were  still  more  characteristic  of  the 


CANADIAN  AND  TRENTON   PERIODS.  215 

period,  and  occur  in  vast  numbers.  Fig.  206  is  Orthis  testu- 
dinaria  ;  Fig.  207,  0.  Occident alis ;  Fig.  208,  Lepcena  sericca. 
There  were  also  some  Lamellibranchs,  as  Fig.  209,  Arnbony- 
ckia  bellistriata  ;  and  some  Gasteropods,  as  Fig.  210,  Raphi- 
stoma  lenticular  is.  Shells  of  Cepbalopods  were  especially 
common  under  the  form  of  a  straight  or  curved  horn  with 
transverse  partitions.  Fig.  211,  Orthoceras  junceum,  repre- 
sents a  small  species.  One  kind  had  a  shell  12  or  15  feet 
long  and  nearly  a  foot  in  diameter.  The  word  Orthoceras  is 
from  the  Greek  6p66s  straight,  and  /cepas  horn. 

There  were  some  species  also  of  the  genus  Nautilus. 

3.  Articulates. — Fig.  212  represents  one  of  the  large  Trilo- 
bites  of  the  Trenton  rocks,  the  Asaphu*  gigas,  —  a  species 
sometimes  found  a  foot  long.  Another  Trilobite  is  the  Caly- 
mene  Mumenbachii,  represented  in  Fig.  148,  page  180. 

While  Trilobites  appear  to  have  been  the  largest  and  high- 
est life  of  the  Primordial  seas,  Cephalopods,  of  the  Orthoceras 
family,  far  exceeded  Trilobites  in  both  respects  in  the  Trenton. 
The  larger  kinds  must  have  been  powerful  animals  to  have 
borne  and  wielded  a  shell  12  or  15  feet  long.  Although 
clumsy  compared  with  the  fishes  of  a  later  age,  they  emu- 
lated the  largest  of  fishes  in  size,  and  no  doubt  also  in  their 
voracious  habits.  Crustaceans,  in  their  highest  divisions,  as 
the  Crabs,  may  perhaps  be  regarded  by  some .  as  of  superior 
rank  to  Cephalopods.  But  Trilobites,  of  the  inferior  division 
of  Crustaceans,  without  proper  legs,  living  a  sluggish  life  in 
slow  movement  over  the  sands  or  through  the  shallow  waters, 
or  skulking  in  holes,  or  attached  like  limpets  to  the  rocks, 
were  far  inferior  species  to  the  Cephalopods. 

3.    General  Observations. 

1.  Geography.  —  The  wide  continental  region  covered  by  the 
Trenton  limestone  formation,  stretching  over  the  Appalachian 
region  on  the  east,  and  widely  through  the  Interior  basin, 
must  have  been  throughout  a  clear  sea,  densely  populated 
over  its  bottom  with  Brachiopods,  Corals,  Crinoids,  Trilobites, 


216  PALEOZOIC   TIME. 

and  the  other  life  of  the  era.  It  may,  however,  have  been  a 
shallow  sea ;  for  the  corals  and  beautiful  shells  of  coral  reefs 
live  mostly  within  100  feet  of  the  surface. 

During  the  later  part  of  the  period,  or  that  of  the  Cincin- 
nati group,  the  same  seas,  especially  on  the  north,  became 
more  open  to  sediment,  through  some  change  of  level  or  of 
coast-barriers,  and  consequently  much  of  the  former  life  dis- 
appeared, and  other  kinds,  adapted  to  impure  waters  or  to 
muddy  bottoms,  supplied  their  places. 

2.  Disturbances  during  the  Lower  Silurian,  and  at  its  Close.  — 
1.  Igneous  ejections  in  the  Lake  Superior  district.  —  During  the 
progress  of  the  Canadian  period  there  were  extensive  igneous 
ejections  through  fractures  of  the  earth's  crust  in  the  vicinity 
of  Lake  Superior,  about  Keweenaw  Point  and  elsewhere ;  and 
probably  to  some  extent  also  over  the  bottom  or  area  of  the 
lake  itself,  for  this  is  indicated  by  the  dikes  and  columnar 
trap  of  Isle  Eoyale,  an  islai  •  in  the  lake.  These  rocks,  which 
were  melted  when  ejected,  now  stand  in  many  places  in  bold 
bluffs  and  ridges ;  and  mixtures  of  scoria  and  sand  make  up 
some  of  the  conglomerate  beds  of  the  region.  The  sandstones, 
penetrated  by  the  dikes  of  trap,  and  made  partly  before  and 
partly  after  the  ejection,  have  a  thickness  in  some  places  of 
six  or  eight  thousand  feet.  The  great  veins  of  native  copper 
of  the  Lake  Superior  region  are  part  of  the  results  of  this 
period  of  disturbance.  The  copper  occurs  in  masses,  sheets, 
strings  and  grains,  all  more  or  less  crystalline,  and  one  sheet 
was  40  feet  long  and  about  200  tons  in  weight. 

2.  Emergence  of  the  region  of  the  Green  Mountains.  —  The 
changes  from  deep  to  shallow  seas,  or  partly  emerged  flats, 
during  the  Silurian  era,  are  evidence  that  changes  of  level, 
by  gentle  movements  or  oscillations  in  the  earth's  crust,  were 
going  on  throughout  it.  But  after  the  Lower  Silurian  had 
closed  there  appear  to  have  been  greater  and  more  permanent 
changes.  The  valley  of  Lake  Champlain  and  the  Hudson,  as  " 
shown  by  Logan,  probably  dates  from  this  time.  The  Green 
Mountains  were  probably  then  made  and  became  part  of  the 


LOWER  SILURIAN.  217 

stable  dry  land,  like  the  Archaean  regions.  (See  map,  page  199.) 
That  they  were  not  dry  land  before  is  shown  by  the  Chazy 
and  Trenton  limestones  in  their  structure,  for  these  are  of 
marine  origin ;  and  that  the  region  was  above  the  water  from 
and  after  this  time  is  indicated  by  the  fact  that  the  Trenton 
formations  were  the  latest  there  formed,  and  by  the  still  more 
important  observation  that  near  Hudson,  in  the  Hudson  Paver 
valley,  and  near  Bernardston,  in  the  Connecticut  Valley,  there 
are  Upper  Silurian  rocks  overlying  unconformably  the  up- 
turned older  rocks. 

During  the  progress  of  the  Lower  Silurian  era  a  great  thick- 
ness of  rock  had  been  made  over  the  Green  Mountain  region, 

-  probably  15,000  or  20,000  feet.    These  beds  were  laid  down, 
not  in  a  sea  15,000  or  20,000  feet  deep  until  it  was  full,  but 
in  shallow  waters  over  a  bottom  that  was  gradually  sinking, 

-  and  so  gradually  that  the  rock-material  accumulating  over 
it  kept  it  shallow.     Then,  when  the  slowly  forming  trough 
had  reached  this  depth,  the  epoch  of  catastrophe,  that  is,  of 
mountain-making,  began  when  the  beds  were  displaced  and 
folded,  and  consolidated  or  crystallized.    Quartzose  sandstones 
were  changed  to  hard  quartzyte,  —  the  rock  of  high  ridges  in 
Berkshire  and  Vermont ;  earthy  sandstones  were  made  into 
mica-schist  and  gneiss ;   and  common  limestones  came  out 
white  or  clouded  marbles,  now  extensively  quarried  for  archi- 
tectural purposes  in  Canaan,  Connecticut,  Berkshire  County 
in  Massachusetts,  and  at  Eutland  and  elsewhere  in  Vermont. 
Thus,  this  northern  end  of  the  Appalachian  region  was  the 
first  of  it  to  be  made  into  mountains  and  become  part  of  tho 
stable  land  :  the  rest  of  it  to  the  south,  as  well  as  the  cen- 
tral region  of  Southern  New  York,  was  still  receiving,  for  a 
long   era   afterward,  new  formations,  and  so  preparing  for 
another  time  of  mountain-making,  —  that  of  the  Alleghany 
range. 

Besides  this  uplifting  and  upturning  in  Western  New  Eng- 
land, there  was  at  the  same  time,  as  shown  by  Safford  and 
Newberry,  a  bending  upward  of  the  Lower  Silurian  beds  along 


218  PALEOZOIC  TIME. 

a  region  extending  southwestward  from  Lake  Erie  over  Cin- 
cinnati through  Kentucky,  which  area  was  partly  an  emerged 
peninsula  or  island  through  the  rest  of  Paleozoic  time. 

In  Great  Britain  and  Europe  also  there  were  disturbances 
at  the  close  of  the  Lower  Silurian.  The  range  of  Southern 
Scotland  has  been  referred  to  this  epoch,  and  so  also  the 
Westmoreland  Hills,  and  mountains  in  North  Wales,  and 
hills  in  Cornwall. 

3.  Life.  —  There  is  no  evidence  that  the  system  of  life  in 
its  progress  during  the  Lower  Silurian  had  so  far  advanced  as 
to  include  a  terrestrial  animal,  or  the  lowest  of  Vertebrates. 
Trilobites  held  the  first  position  in  the  Primordial  Period,  Or- 
thocerata  and  other  Cephalopods  in  the  Trenton.  Among 
Articulates  there  were  neither  Myriapods,  Spiders,  nor  In- 
sects as  far  as  discovered ;  for  these  are  essentially  terrestrial 
animals,  and  the  first  species  of  them  thus  far  found  are  of 
Devonian  age. 

Among  the  genera  of  the  Lower  Silurian,  only  five  have 
living  species.  These  are  Lingula,  Discina,  Rhynchonella,  and 
Crania  among  Brachiopods,  and  Nautilus  among  Cephalopods. 
The  Linfjulcc  of  the  Primordial  are  referred  to  another  genus  ; 
but  true  species  of  the  genus  Lingula  are  reported  from  the 
Trenton.  These  genera  of  long  lineage  thus  reach  through 
all  time  from  the  Lower  Silurian  onward.  All  other  genera 
disappear,  —  some  at  the  close  of  the  Primordial,  others  at 
that  of  the  Canadian  or  Trenton  period,  and  some  at  the  ter- 
mination of  subordinate  epochs  within  these  periods. 

The  extermination  of  species  took  place  at  intervals 
through  the  periods,  as  well  as  at  their  close ;  though  those 
at  the  latter  were  most  universal.  With  the  changes  from 
one  stratum  to  another  there  were  disappearances  of  some 
species,  and  with  the  changes  from  one  formation  to  another 
still  larger  proportions  became  extinct.  No  Primordial  spe- 
cies are  known  to  occur  in  the  Canadian  period ;  very  few  of 
the  species  of  the  Canadian  period  survive  into  the  Trenton ; 
and  very  many  of  those  of  the  early  part  of  the  Trenton  did 


UPPER  SILURIAN.  219 

not  exist  in  the  later  part.  Thus  life  and  death  were  in  pro- 
gress together,  species  being  removed,  and  other  species  ap- 
pearing as  time  moved  on. 

3.    Upper  Silurian  Era. 
I.    Subdivisions. 

The  Upper  Silurian  era  in  North  America  includes  four 
periods :  the  NIAGARA,  the  SALINA,  the  LOWER  HELDERBERG, 
and  the  ORISKANY.  The  name  of  the  first  is  from  the  Niagara 
River,  along  which  the  rocks  are  displayed ;  that  of  the  second, 
from  Salina  in  Central  New  York,  the  beds  being  the  salt- 
bearing  rocks  of  that  part  of  the  State;  that  of  the  third, 
from  the  Helderberg  Mountains,  south  of  Albany,  where  the 
lower  rocks  are  of  this  period ;  that  of  the  fourth,  from  Oris- 
kany,  a  place  in  Central  New  York,  northwest  of  Utica. 

2.    Rocks:   Kinds  and  Distribution. 

The  rocks  of  the  Niagara  period  are  :  1.  A  conglomerate 
and  grit-rock  called  the  Oneida  conglomerate,  which  extends 
from  Central  New  York  southward  along  the  Appalachian 
region,  having  a  thickness  of  700  feet  in  some  parts  of  Penn- 
sylvania ;  together  with  shaly  sandstones  of  the  Medina  group, 
which  spread  westward  from  Central  New  York  through 
Michigan,  and  also  southward  along  the  Appalachian  region, 
being  1,500  feet  thick  in  Pennsylvania;  2.  Hard  sandstones, 
or  flags  and  shales  of  the  Clinton  group,  having  nearly  the 
same  distribution  as  the  Medina  formation,  though  a  little 
more  widely  spread  in  the  west,  and  about  2,000  feet  thick 
in  Pennsylvania ;  3.  The  Niagara  group,  occurring  in  Western 
New  York,  and  extending  widely  over  both  the  Appalachian 
and  Interior  Continental  regions :  it  consists,  at  Niagara,  of 
shales  below  and  thick  limestone  above ;  mainly  of  limestone 
in  the  Interior  region ;  and  of  clayey  sandstone  or  shales  in 
the  Appalachian  region,  where  it  has  a  thickness  of  1,500 
feet  or  more.  The  Niagara  is  one  of  the  great  limestone 


PALEOZOIC  TIME. 
»ns   of    the   continent,   existing   also   in  the    Arctic 

Eipple-marks  and  mud-cracks  are  very  common  in  the 
Medina  formation.  The  example  of  rill-marks  figured  on 
page  46  is  from  its  strata  in  Western  New  York. 

The  Salina  rocks  are  fragile,  clayey  sandstones,  marlytes, 
and  shales,  usually  reddish  in  color,  and  including  a  little 
limestone.  They  occur  in  New  York  and  sparingly  to  the 
westward,  being  thickest  (700  to  1,000  feet  thick)  in  Onon- 
daga  County,  New  York. 

The  salt  of  Salina  and  Syracuse,  in  Central  New  York,  is 
obtained  from  wells  of  salt  water  150  feet  and  upward  in 
depth,  which  are  borings  into  these  saliferous  rocks.  From  35 
to  45  gallons  of  the  water  afford  a  bushel  of  salt,  while  of 
sea-water  it  takes  350  gallons  for  the  same  amount.  No  solid 
salt  is  there  found;  but  farther  west,  near  Wyoming  and 
Warsaw,  N.  Y.,  a  bed,  50  to  100  feet  thick,  occurs  at  a  depth 
of  1,200  to  1,500  feet;  and  near  Goderich,  in  Canada,  at  a 
depth  of  about  1,000  feet,  a  bed  14  to  40  feet  thick.  Gypsum 
is  common  in  some  of  the  beds. 

The  Lower  Heldcrberg  group  consists  mainly  of  limestones, 
and  is  the  second  limestone  formation  of  the  Upper  Silurian. 
The  formation  is  well  developed  in  the  State  of  New  York 
and  along  the  Appalachian  region  to  the  south ;  it  also  occurs 
in  Ohio,  Indiana,  Southern  Illinois,  and  Tennessee ;  also 

Fig.  213. 


w 

Section  along  the  Niagara,  from  the  Falls  to  Lewlston  Heights. 

along  the  Connecticut  Valley,  in  Northern  Maine,  and  in 
New  Brunswick  and  Nova  Scotia. 

The  section,  Fig.  213,  represents  the  rocks  on  the  Niagara 


UPPER  SILURIAN.  221 

River  at  and  below  the  Falls.  The  Falls  are  at  F ;  the  whirl- 
pool, three  miles  below,  at  W ;  and  the  Lewiston  Heights, 
which  front  Lake  Ontario,  at  L.  Nos.  1,  2,  3,  4  are  different 
sandstone  strata  belonging  to  the  Medina  group;  5,  shale, 
and  6,  limestone,  to  the  Clinton  group ;  7,  shale,  and  8,  lime- 
stone, to  the  Niagara  group.  The  next  section  (Fig.  214), 

Fig.  214. 


G 
Section  of  the  Salina  and  underlying  strata,  from  north  to  south,  south  of  Lake  Ontario. 

from  the  region  south  of  the  eastern  part  of  Lake  Ontario, 
consists  as  follows :  5  b,  Medina  group,  5  c,  Clinton  group, 
5d,  Niagara  group  (shale  and  limestone),  G,  Salina  beds. 
(Hall.) 

The  Oriskany  beds  are  mostly  rough  sandstones.  The  for- 
mation extends  from  Oriskany,  New  York,  southward  along 
the  Appalachian  region  through  Pennsylvania,  Maryland,  and 
Virginia,  where  it  is  several  hundred  feet  thick.  It  occurs 
also  in  Northern  Maine,  and  at  Gasp4  on  the  Gulf  of  St. 
Lawrence,  where  the  rock  is  partly  limestone. 

In  Great  Britain  the  Upper  Silurian  rocks  are  first  sand- 
stones and  shales,  called,  where  occurring  in  South  Wales, 
Llandovery  beds,  and  corresponding  to  the  Medina  and  Clin- 
ton groups.  Above  these  there  is  the  Wenlock  limestone 
group,  consisting  of  limestone  and  some  shale  (and  including, 
in  the  upper  portion,  the  Dudley  limestone).  These  rocks 
occur  as  surface-rocks  near  the  borders  of  Wales  and  England. 
Next  comes  the  Ludlow  group,  of  the  age  of  the  Lower  Hel- 
derberg  and  Oriskany  beds. 

In  Scandinavia  the  Gothland  limestone  is  the  equivalent 
of  the  Niagara. 

3.    Life. 

The  limestone  strata  and  most  of  the  other  beds  of  the 
Niagara  group  are  full  of  fossils ;  and  so  also  are  the  rocks  of 


222 


PALEOZOIC  TIME. 


the  Lower  Helderberg  period,  and  of  the  Wenlock  and  Lud- 
low  formations  in  Great  Britain.  Nearly  all  of  the  Salina 
formation  is  destitute  of  them. 

The  life  of  the  era  was  the  same  in  general  features  as  that 
of  the  latter  half  of  the  Lower  Silurian,  though  mostly  dif- 
ferent in  species. 


Figs.  215-227. 
215 


219 


RADIATES:  Fig.  215,  Zaphrentis  bilateralis,  Clinton  group  ;  216,  Favosites  Niagarensis, 
Niagara  group  ;  217,  Halysites  catenulata,  id.  ;  218,  Caryocrinus  ornatus,  id.  —  MOL- 
LUSKS  :  Fig.  219,  Peritainerus  oblongus,  Clinton  gr.  ;  220,  Ortuis  varica(x  2),  Niagara 
gr.j  and  Dudley  limestone  ;  221,  Leptsena  transversalis,  id. ;  222,  Strophomena  rhomboida- 
lis,  id. ;  223,  Rhynchotreta  cuneata,  U.  S.  and  Great  Britain,  id.  ;  224,  Pterinea  emacerata. 
Niagara  gr.  ;  225,  Cyclonema  cancellata,  Clinton  gr.  ;  226,  Platyceras,  angulatum,  Niagara 
gr.  — ARTICULATES  :  Fig.  227,  Homalonotus  delphinocephalus,  id. 

The  only  plants  yet  found  in  the  Lower  Helderberg  and 
underlying  beds  are  Algce,  or  Sea-weeds ;  but  in  the  Oriskany 


UPPER  SILURIAN.  223 

beds  of  Gaspe  are  found  remains  of  true  terrestrial  species,  re- 
lated to  the  Lycopods  or  modern  Ground-pine.  They  were 
about  as  large  as  the  common  Lycopodium  dendroideum  of  the 
present  day.  (Seepage  188.)  Similar  remains  of  plants  have 
been  found  also  in  the  Upper  Ludlow  beds  of  Great  Britain. 

In  the  Animal  Kingdom  the  sub-kingdom  of  Radiates  was 
represented  most  prominently  by  Corals  and  Crinoids;  that 
of  Mollusks,  by  species  of  all  the  grand  divisions,  among  which 
the  Brachiopod  and  Orthoceras  tribes  were  the  most  character- 
istic; and  especially  the  Brachiopod,  whose  shells  far  outnum- 
ber those  of  all  other  Mollusks  ;  that  of  Articulates,  by  Worms, 
Ostracoids,  and  Trilobites;  and,  before  the  close  of  the  era,  by 
the  new  form  of  Crustaceans  represented  in  Fig.  235. 

1.  Radiates.  —  Fig.  215  is  a  polyp-coral  of  the  Cyatlwphyl- 
loid  tribe,  showing  the  radiating  plates  of  the  interior ;  Fig. 
216,  a  species  of  Favositcs,  a  genus  in  which  the  corals  have  a 
columnar  structure  (somewhat  honey  comb -like,  whence  the 
name  from  the  Latin  favus,  honeycomb),  and  horizontal  parti- 
tions subdivide  the  cells  within;  Fig.  217,  Haly sites  catenulata, 
called  chain-coral ;  Fig.  218,  a  Crinoid,  Caryocrinus  ornatus, 
the  arms  at  the  summit  broken  off;  Fig.  164,  page  183,  another 
Crinoid  of  the  family  of  Cystideans,  from  the  Niagara  group ; 
Fig.  162,  page  183,  a  star-fish,  also  from  the  Niagara  group. 

2.  Mollusks.— Figs.  219  to  223,  different  Brachiopods  of 
the  Niagara  period;  Figs.  228  to  234,  other  species  charac- 
teristic of  the  Lower  Helderberg  period  ;  Figs.  225,  226,  Gas- 
teropods;  and  Fig.  224,  a  Lamellibranch  of  the  Niagara  period. 
Fig.  233  represents  small  slender  tubular  cones,  called  Tcntac- 
ulites,  which  almost  make  up  the  mass  of  some  layers  in  the 
Lower  Helderberg;  the  form  of  one  enlarged  is  shown  in  Fig. 
234;  they  are  regarded  as  the  shells  of  Pteropods. 

3.  Articulates. — Fig.  227  is  a  reduced  figure  of  a  common 
Trilobite  of   the  Niagara  group,  a  species  of   Homalonotus, 
often  having  a  length  of  8  or  10  inches.     Fig.  235  repre- 
sents Eurypterus  remipes,  a  species  of  a  family  of  Crustaceans, 
occurring  first  in  the  Utica  shale ;  it  is  sometimes  nearly 


224 


PALEOZOIC   TIME. 


a  foot  long. 


Species  of  the  same  family  occur  in  Great 
Britain  in  the  Ludlow  beds,  and  one  of  them  is  supposed, 
from  the  fragments  found,  to  have  been  6  or  8  feet  long, 
far  surpassing  any  Crustacean  now  living;  Fig.  236,  an 
Ostracoid  Crustacean,  the  Lcperditia  alta,  of  unusually 
large  size  for  the  family,  modern  Ostracoids  seldom  exceed- 
ing a  twelfth  of  an  inch  in  length. 

Figs    228-236 


MOLLUSKS  :  Figs.  228,  229,  Pentamerus  galeatus ;  230,  231,  Rhynchonella  ventricosa  ; 
232,  Spirifer  macropleurus  ;  233,  Tentaculites  irregularis  ;  234,  id  enlarged.  —ARTICU- 
LATES :  Fig.  235,  Eurypterus  remipes,  a  small  specimen  ;  236,  Leperditia  alta.  Species 
all  from  the  Lower  Helderberg  group. 

4.  Vertebrates.  —  The  first  remains  of  Vertebrates  yet  dis- 
covered occur  in  the  Upper  Silurian.  They  are  of  fishes,  and 
have  been  found  in  the  Ludlow  beds  of  Great  Britain.  They 
are  teeth,  scales,  and  other  relics,  chiefly  of  shark-like  species. 
The  kinds  are  further  described  under  the  Devonian. 


4.  General  Observations. 


1.  Geography,  —  On  the  map,  page  195,  the  areas  over  which 
the  Silurian  formations  are  surface-rocks  are  distinguished  by 


UPPEK  SILURIAN.  225 

being  horizontally  lined.  It  is  observed  that  they  spread 
southward  from  the  northern  Archaean  area,  and  indicate  an 
extension  in  that  direction  of  the  growing  continent. 

South  of  the  Silurian  area  commences  the  Devonian,  which 
is  vertically  lined;  and  the  limit  between  them  shows  ap- 
proximately the  course  of  the  sea-shore  at  the  close  of  the 
Silurian  age.  It  is  seen  that  more  than  half  of  New  York, 
and  nearly  all  of  Canada  and  Wisconsin,  had  by  that  time 
become  part  of  the  dry  land ;  but  a  broad  bay  covered  the 
Michigan  region  to  the  northern  point  of  Lake  Michigan, 
for  here  Devonian  rocks,  and  to  some  extent  Carboniferous, 
were  afterward  formed.  The  Archaean  dry  land,  the  nucleus 
of  the  continent,  had  also  received  additions  in  a  similar 
manner  on  its  eastern  and  western  sides,  through  British 
America.* 

But,  with  all  the  increase,  the  amount  of  dry  land  in  North 
America  was  still  small.  Europe  is  proved  by  similar  evi- 
dence to  have  had  much  submerged  land.  The  surface  of  the 
earth  was  a  surface  of  great  waters,  with  the  continents  only 
in  embryo,  —  one  large  area  and  some  islands  representing 
that  of  North  America,  and  an  archipelago  that  of  Europe. 
The  emerged  land,  moreover,  was  most  extensive  in  the 
higher  latitudes.  The  rivers  of  a  world  so  small  in  its  lands 
must  also  have  been  small.  The  lands,  too,  according  to 
present  evidence,  had  no  green  sward  over  the  rocks,  except 
during  the  closing  part  of  the  Silurian  age. 

The  succession  of  Upper  Silurian  formations  is  as  follows  : 
1.  The  Medina  sandstone  having  at  base  the  coarse  grit  called 
Oneida  conglomerate,  occurring  of  great  thickness  along  the 
Appalachian  region,  and  reaching  north  to  Central  New  York, 

*  On  the  map  referred  to,  page  195,  lines  of  the  Silurian  and  Devonian  are 
seen  to  extend  from  the  Hudson  River  southwestward  along  the  Appalachian 
region.  But  the  outcrop  of  the  Silurian,  here  represented,  is  not  evidence 
that  there  was  a  strip  of  dry  land  along  this  region  from  the  close  of  the  Silu- 
rian era,  because  there  is  proof  that  these  Appalachian  outcrops  are  a  conse- 
quence of  the  uplift  of  the  Alleghany  Mountains,  an  event  of  much  later 
date.  (Page  277.) 

15 


226  PALEOZOIC  TIME. 

and,  besides,  spreading  westward  beyond  the  limits  of  that 
State ; '  2.  The  Clinton  group  of  flags  and  shales,  having 
the  same  Appalachian  extension  and  great  thickness,  but 
spreading  on  the  north  much  farther  westward,  even  to  the 
Mississippi;  3.  The  Niagara  group,  covering  the  Appalachian 
region  deeply  with  sandstones  and  shales,  and  New  York  with 
shales  and  limestones,  and  spreading  as  a  great  limestone 
formation  through  the  larger  part  of  the  Interior  region;  then 
(4)  the  limited  Salina  salt-bearing  marlytes  of  New  York,  ex- 
tending west  through  Canada,  and  over  part  of  the  Appala- 
chian region  southwest ;  then  (5)  another  limestone,  but  im- 
pure, spreading  over  New  York  State  and  the  Appalachian 
region,  and  also  some  of  the  States  west ;  and  also  occurring 
in  the  Connecticut  Valley  and  over  Maine  to  the  Gulf  of  St. 
Lawrence.  These  facts  teach  that  geographical  changes  took 
place  from  time  to  time,  in  the  course  of  the  era,  corresponding 
to  these  several  changes  in  the  formations.  The  clear  conti- 
nental seas  of  the  Trenton  period  were  succeeded  by  con- 
ditions fitted  to  produce  the  several  arenaceous  and  argilla- 
ceous formations,  of  varying  limits,  which  followed  ;  but  clear 
waters  returned  again  at  the  epoch  of  the  Niagara  group,  when 
corals,  crinoids,  and  shells  covered  the  bottom  of  the  conti- 
nental sea  and  made  the  Niagara  limestone  formation.  But 
these  seas  in  the  Niagara  epoch  were  less  extended  than  those 
of  the  Trenton ;  for  the  Appalachian  region,  instead  of  being 
part  of  the  pure  sea  and  making  limestones,  was  receiving 
great  depositions  of  sand  and  clay,  as  if  it  were  at  the  time 
a  broad  reef,  or  bank,  border'  ig  the  Atlantic  Ocean. 

The  Niagara  epoch  of  limestone-making  was  followed  by 
the  Salina  or  saliferous  period.  Since  the  beds  are  (1)  clays 
and  clayey  sands,  (2)  are  almost  wholly  without  fossils,  arid 
(3)  afford  salt,  it  may  be  inferred  that  Central  New  York  was 
at  the  time  a  great  salt  marsh,  mostly  shut  off  from  the  sea. 
Over  such  an  area  the  waters  would  at  times  have  become  too 
salt  to  support  life,  owing  to  partial  evaporation  under  the 
hot  sun,  and  too  fresh  at  other  times,  from  the  rains.  More- 


UPPER  SILURIAN.  227 

over,  muddy  deposits  would  have  been  formed ;  for  they  are 
now  common  in  salt  marshes  wherever  there  is,  as  there  was 
then,  no  covering  of  vegetation,  and  the  salt  waters  would 
naturally  have  yielded  salt  on  evaporation  in  the  drier  sea- 
sons. Through  an  occasional  ingress  of  the  sea,  the  salt 
waters  might  have  been  resupplied  for  further  evaporation. 

There  is  direct  testimony  as  to  the  condition  of  the  land 
and  shallowness  of  the  waters  in  the  regions  where  many 
of  the  rocks  were  in  progress;  for  ripple-marks  and  mud- 
cracks  are  common  in  some  layers,  and  are  positive  evidence 
that  the  sands  and  earth  that  are  now  the  solid  rock  were 
then  the  loose  sands  of  beaches,  sand-flats,  or  sea-bottoms,  or 
the  mud  of  a  salt  marsh.  Such  little  markings,  therefore, 
remove  all  doubt  as  to  the  condition  of  Central  New  York  in 
the  Salina  period. 

Similar  markings  indicate,  also,  the  precise  condition  of 
the  region  of  the  Medina  sandstone,  showing  that  there  were 
sand-flats,  sea-beaches,  and  muddy  bottoms  open  to  the  in- 
flowing sea.  Where  the  rill-marks  were  made  (Fig.  24,  page 
46)  the  sands  of  the  spot  were  those  of  a  gently  sloping  flat 
or  beach ;  the  waters  swept  lightly  over  the  sands,  dropping 
here  and  there  a  stray  shell  (as  the  Lingula  cuneata)  or  a 
pebble,  which  became  partly  buried;  and  then,  as  they 
retreated,  they  made  a  tiny  plunge  over  the  little  obstacle 
and  furrowed  out  the  loose  sand  below  it.  The  fineness  of 
the  sand,  lightness  of  the  shells,  and  smallness  of  the  furrows 
are  proof  that  the  movements  were  light. 

The  great  thickness  of  the  several  formations  of  the  Upper 
Silurian  along  the  Appalachian  region  leads  to  many  inter- 
esting conclusions.  It  has  been  stated  (page  217)  that  the 
Appalachian  formations  of  the  earlier  Silurian  were  equally 
remarkable  for  their  great  thickness.  The  Appalachian  re- 
gion, from  the  Primordial  era  onward,  was,  hence,  in  strong 
contrast  with  the  Interior  Continental  region,  where  the 
series  of  cotemporaneous  beds  are  hardly  one  tenth  as  thick. 
Taking  this  into  connection  with  another  fact,  that  very 


228  PALEOZOIC  TIME. 

many  of  the  strata  among  the  thousands  of  feet  of  Silurian 
formations  in  the  Appalachian  region  contain  those  evidences 
of  shallow  water  and  mud-flat  or  sand-flat  origin  above  ex- 
plained, there  is  full  proof  that  in  the  Silurian  era  the  region 
was  for  the  most  part,  as  already  suggested,  a  vast  sand-reef, 
ever  increasing  by  new  accumulations  under  the  action  of  the 
waves  and  currents  of  the  ocean.  It  was  much  of  the  time  a 
great  barrier-reef  lying  between  the  open  ocean  and  the  Inte- 
rior Continental  sea ;  and  under  its  lee,  this  inner  sea,  opening 
southward  through  the  area  of  the  Mexican  Gulf,  was  often 
in  the  best  condition  for  the  growth  of  the  Shells,  Corals,  and 
Crinoids  of  which  the  great  limestones  were  made. 

While  the  Appalachian  region  was  alike  in  its  general  con- 
dition through  the  earlier  and  later  Silurian,  the  limits  of  the 
formations  in  progress  during  these  two  eras  were  somewhat 
different,  as  explained  on  page  217.  The  part  of  the  Appala- 
chian region  which  participated,  during  the  Upper  Silurian 
era,  in  the  great  changes  connected  with  the  formation  of 
rocks,  extended  northward  from  Pennsylvania. into  New  York, 
and  not  along  the  Green  Mountains ;  the  rocks  in  the  State 
of  New  York  have  great  thickness  for  some  distance  beyond 
the  Pennsylvania  border,  but  thin  out  about  the  centre. 

2.  Life.  —  In  the  Upper  Silurian  the  highest  species  of  the 
seas  and  of  the  world  continued  for  a  while  to  be  Mollusks, 
of  the  order  of  Cephalopods.  But  before  its  close  there  were 
fishes  in  the  waters,  and  Vertebrates  ever  afterward  existed  as 
the  highest  species.  Corals  and  Crinoids  were  the  only  kinds 
of  life  that  had  the  semblance  of  flowers.  These  flower-ani- 
mals foreshadowed  the  flowers  of  the  vegetable  kingdom  for 
ages  before  any  of  the  latter  existed.  The  Lycopods  of  the 
later  part  of  the  Upper  Silurian  were  flowerless  plants,  like 
the  Ferns. 

Up  to  1872,  over   10,000  species  of   Silurian  animals  — 
ranging  from  Sponges  to  Fishes  —  had  been   made   known 
through  the  study  of  fossils. 


DEVONIAN  AGE.  229 


II.    AGE    OF    FISHES,   or    DEVONIAN    AGE. 
I.   Subdivisions. 

The  Devonian  formation  was  so  named  by  Sedgwick  and 
Murchison,  from  Devonshire,  England,  where  it  occurs. 

The  Age  may  be  divided  into  two  eras,  -  —  an  earlier  and  a 
later,  or  that  of  the  lower  and  that  of  the  upper  formations. 
The  Lower  Devonian  includes  the  CORNIFEROUS  period  ;  the 
Upper  Devonian,  the  HAMILTON,  CHEMUNG,  and  CATSKILI 
periods. 

2.    Rocks:   Kinds  and  Distribution. 

1.  Earlier  and  Later  Eras.  —  The  Lower  Devonian  is  remark- 
able for  a  great  limestone  formation,  which  spread  from  New 
York  over  a  large  part  of  the  Interior  region,  and  nearly 
equalled  the  Trenton  in  extent;  while  the  Upper  includes 
very  little    limestone,  the   rocks   being   mainly   sandstones, 
shales,  and  conglomerates. 

2.  Corniferous  Period.  —  The  lowest  rocks  of  this  period  are 
fragmental  beds,  called  the  Cauda-Galli  grit  and  the  ScJio- 
harie  grit,  having  their  distribution  along  the  Appalachian 
region,  commencing  in  Central  and  Eastern  New  York  and 
extending  southwestward. 

Next  follows  the  great  Corniferous  limestone,  the  lower 
part  of  which  is  sometimes  called  the  Onondaga  limestone, 
and  the  whole  often  the  Upper  Helderberg  group.  It  stretches 
from  Eastern  New  York  westward  to  the  States  beyond  the 
Mississippi. 

The  name  Corniferous  (derived  from  the  Latin  cornu,  horn) 
was  given  it  by  Eaton,  from  its  frequently  containing  a  kind 
of  flint  called  hornstone.  This  hornstone  differs  from  true 
flint  in  being  less  tough,  or  more  splintery  in  fracture,  though 
it  is  like  it  in  hardness  and  in  consisting  wholly  of  silica. 

The  limestone  is  in  many  places  literally  an  ancient  coral 
reef.  It  contains  corals  in  vast  numbers  and  of  great  variety  ; 


230  PALEOZOIC  TIME. 

and  in  some  places,  as  at  the  Falls  on  the  Ohio,  near  Louis- 
ville, Kentucky,  the  resemblance  to  a  modern  reef  is  perfect. 
Some  of  the  coral  masses  at  that  place  are  5  or  6  feet  in  di- 
ameter ;  and  single  polyps  of  the  Cyathophylloid  corals  had 
in  some  species  a  diameter  of  2  and  3  inches,  and  in  one,  of  6 
or  7  inches. 

The  same  reef-rock  occurs  near  Lake  Memphremagog  on 
the  borders  of  Vermont  and  Canada,  and  also  at  Littleton, 
New  Hampshire;  but  the  corals  have  in  these  places  been 
partly  obliterated  by  metamorphism. 

3.  Hamilton  Period.  —  The  Hamilton  formation  consists  in 
New  York  of  sandstones  and  shales,  with  a  few  thin  layers  of 
limestone.     It  consists  of  three  parts,  corresponding  to  three 
epochs :  the  lower  part  is  called  the  Marcellus  shale ;  the 
middle,  the  Hamilton  beds  ;  and  the  upper,  the  Genesee  shale. 
It  has  its  greatest  thickness  along  the  Appalachians.     From 
New  York  it  spreads  westward,  where  it  is  in  part  calcareous, 
and  forms  the  upper  part  of  the  "cliff"  limestone.     It  in- 
cludes a  stratum  of  black  shale  (supposed  to  be  of  the  epoch 
of  the  Genesee  shale),  100  to  350  feet  thick,  which  yields  in 
some  places  15  to  20  per  cent  of  mineral  oil.     The  formation 
occurs  also  in  Eastern  Maine,  New  Brunswick,  and  at  Gaspe, 
on  the  Gulf  of  St.  Lawrence. 

The  Hamilton  beds  afford  an  excellent  flagging-stone  in 
Central  New  York,  and  on  the  Hudson  River,  near  Kingston, 
Saugerties,  Coxsackie,  and  elsewhere,  which  is  extensively 
quarried  and  exported  to  other  States. 

4.  Chemung  Period.  —  The  Chemung  beds  are  mainly  sand- 
stones, or  shaly  sandstones,  with  some  conglomerate.     They 
spread  over  a  large  part  of  Southern  and  Western  New  York, 
having  great  thickness  in  the  Catskill  Mountains.     A  shale 
of  the  period  in  Northern  Ohio  is  called  the  Erie  shale. 

The  formation  along  the  Appalachians  is  5,000  feet  thick. 
It  thins  out  to  the  west  of  New  York,  in  Ohio,  and  Michigan. 

In  the  following  section,  taken  on  a  north-and-south  line 
south  of  Lake  Ontario,  No.  6  represents  the  beds  of  the 


DEVONIAN  AGE.  231 

Salina  period ;  overlaid  by  7,  the  Lower  Helderberg  lime- 
stone ;  9,  the  Corniferous,  or  Upper  Helderberg  limestone ; 
10,  a,  b,  c,  the  Hamilton  beds;  and  11,  the  Cheinung  group. 

Fig.   237 

1 1 

(T  7          = 9  10  a 

Section  of  Devonian  formations  south  of  Lake  Ontario. 

5.  Catskill  Period.  —  The  rocks  are  sandstones,  shaly  sand- 
stones, and  shales ;  they  occur  in  Eastern  New  York,  and  are 
2,000  to  3,000  feet  thick  in  the  Catskill  Mountains.  They 
also  extend  southwestward  along  the  Appalachians,  being 
5,000  to  6,000  feet  thick  in  Pennsylvania. 

In  Great  Britain  the  Devonian  rocks  include  the  Old  Red 
Sandstone,  the  prevailing  rock  of  the  age  in  Wales  and  Scot- 
land. The  thickness  in  some  places  is  8,000  to  10,000  feet. 
This  formation,  besides  sandstone,  includes  marly tes  of  red  and 
other  colors,  and  some  limestone.  The  distribution  in  Great 
Britain  is  shown  on  the  map,  page  244.  In  Germany,  in  the 
Rhenish  provinces,  there  is  a  coral  limestone  very  similar  to 
that  of  North  America. 

3.    Life. 
1.    General  Characteristics. 

The  Devonian  of  North  America  was  characterized  by 
forests  and  an  abundance  of  insects  over  the  land,  and 
by  fishes  of  many  kinds  in  the  waters. 

2.    Plants. 

Figs.  238-240  represent  portions  of  some  of  the  plants. 
Fig.  240  is  a  fragment  of  a  Fern,  and  Figs.  238,  239,  portions 
of  the  trees,  of  the  age.  The  scars  or  prominences  over  the 
surface  are  the  bases  of  the  fallen  leaves ;  a  dried  branch  of 
a  Norway  spruce,  stripped  of  its  leaves,  looks  closely  like 
Fig.  239.  By  referring  to  page  186,  it  will  there  be  seen  that 


232 


PALEOZOIC   TIME. 


among  the  Cryptogams  there  is  one  order,  the  highest,  or 
that  of  Acrogens,  in  which  the  plants  have  upward  growth 


Figs.  238-240 


PLANTS.  —  Fig.  238,  Lepidodendron  primsevum,  from  the  Hamilton  group ;  239,  Sigillaria 
Hallii,  ibid. ;  240,  Noeggerathia  Halliana,  from  the  Chemuug  group. 

like  ordinary  trees,  and  the  tissues  are  partly  vascular :  it  is 
the  one  containing  the  Ferns,  Lycopods,  and  Equiseta  or  Horse- 
tails. The  most  ancient  of  land  plants  belong,  to  a  great  ex- 
tent, to  this  order,  —  the  highest  of  Cryptogams,  and  were  of 
the  three  kinds  just  mentioned.  Another  portion  are  related 
to  the  lowest  order  of  flower-bearing  plants  or  Phenogams, 
called  Gymnosperms  (see  page  188). 

The  groups  represented  under  these  divisions  are  the  fol- 
lowing:— 

I.    Flowerless    Plants,   or  Cryptogams,   Order   of 
Acrogens. 

1.  Fern  Tribe.  —  The  species  have  a  general  resemblance  to 
the  ferns  or  brakes  of  the  present  time. 

2.  Lycopods,  or  plants  related  to  the  Ground-Pine.  —  The 
existing  plants  of  this  tribe  are  slender  species,  seldom  over  4 
or  5  feet  high :  some  of  the  ancient  kinds  were  of  the  size  of 


DEVONIAN   AGE.  233 

forest-trees.  These  ancient  species  belong  mostly  to  the  Lepi- 
dodendron  family,  in  which  the  scars  are  contiguous  and  are 
arranged  in  quincunx  order,  that  is,  alternate  in  adjoining 
rows,  as  shown  in  Fig.  238.  The  name  Lepidodendron  is 
from  the  Greek  Xevrt?,  scale,  and  Sev&pov,  tree,  and  alludes  to 
the  scar-covered  trunk,  which  looks  something  in  surface  like 
a  scale-covered  reptile.  The  Ground-Pine  of  modern  woods, 
although  flowerless  like  the  fern,  has  leaves  very  similar  to 
those  of  the  Spruce  or  Cedar  (Conifers) ;  and  this  type  of 
plants  is  intermediate  in  some  respects  between  the  Aero- 
gens  and  Gymnosperms  (Conifers). 

The  Sigillarids,  another  family  in  this  tribe,  included  trees 
of  moderate  height,  with  stout,  sparingly  branched  trunks, 
bearing  long  linear  leaves  much  like  those  of  the  Lepidoden- 
drids  ;  but  the  scars  on  the  exterior  are  mostly  in  parallel 
vertical  lines,  as  in  Fig.  239,  and  Fig.  283,  page  251,  and  not 
in  quincunx  order,  like  those  of  the  Lepidodendra.  The  name 
is  from  the  Latin  sigillum,  a  seal,  in  allusion  to  the  scars. 

3,  Equisetum,  or  Horse-tail  Tribe.  —  The  Equiseta  of  mod- 
ern wet  woods  are  slender,  hollow,  jointed  rushes,  called 
sometimes  scouring-rushes.  They  often  have  a  circle  of  slen- 
der leaf-like  appendages  at  each  joint.  The  Calamites  or  Tree- 
rushes,  which  are  referred  to  this  tribe,  are  peculiar  to  the 
ancient  world,  none  having  existed  since  the  Mesozoic.  They 
had  jointed  striated  stems  like  the  Equiseta,  and  otherwise 
resembled  them.  But  they  were  often  a  score  of  feet  or  more 
in  height,  and  over  6  inches  in  diameter.  Some  of  them  had 
hollow  stems  like  the  Equiseta ;  others  had  the  interior  of  the 
stems  partially  woody,  and  these  were  intermediate  in  some 
respects  between  the  Equiseta  and  the  Gymnosperms.  Fig. 
286,  page  251,  represents  a  portion  of  one  of  these  plants. 

II.  Flowering  Plants,  or  Phenogams,  of  the  Order 
of  Gymnosperms. 

Conifers.  —  The  species  are  related  to  the  common  Pines 
and  Spruces,  or  more  nearly  to  the  Araucanian  Pines  of  Aus- 


234 


PALEOZOIC  TIME. 


tralia  and  South  America.     The  fossils  are  merely  portions  of 
the  trunk  or  branches. 

Conifers,  Ferns,  and  Lepidodendrids  have  also  been  reported. 
from  some  of  the  Devonian  beds  of  Britain  and  Europe. 

The  hornstone,  which  is  massive  quartz,  or  silica,  develops, 
under  the  microscope,  the  fact  that  it  was  probably  made 
from  the  siliceous  remains  of  plants  and  animals.  Figs.  241 
to  255  represent  some  of  the  species  which  have  been  detected 
by  Dr.  M.  C.  White  in  specimens  from  New  York  and  else- 
where. Figs.  241  to  247  are  microscopic  plants,  related  to 


Figs.  241-255. 


241 


2f,t 


Microscopic  Organisms  from  the  Hornstone. 

the  Dcsmids ;  Fig.  248  is  another  kind,  called  a  Diatom,  a 
kind  which  forms  siliceous  shells,  and  which  is  probably  one 
of  the  sources  of  the  silica  of  which  the  hornstone  was  made. 
(See,  on  Diatoms  and  Desmids,  pages  68  and  187.)  Figs. 
249,  250  are  spicules  of  Sponges,  also  siliceous,  and  another 
of  the  sources  of  the  silica.  Figs.  251,  252  are  probably  also 
sponge-spicules.  Figs.  254,  255  are  fragments  of  the  teeth 
of  some  Gasteropod  Mollusk.  The  last  is  from  a  hornstone 
of  the  Trenton  period  which  was  found  to  afford  the  same 
evidences  of  organic  origin. 

3.  Animals. 

The  early  Devonian  was  the  coral  period  of  the  ancient 
world.  In  no  age  before  or  since,  not  even  the  present,  have 
coral  reefs  of  greater  extent  been  formed. 

Among  Mollusks,  Brachiopods  were  still  the  prevailing 
kinds,  though  ordinary  Bivalves  or  Lamellibranchs,  and 


DEVONIAN  AGE. 


235 


Univalves  or  Gasteropoda,  were  more  abundant  than  in 
the  Silurian.  A  new  type  of  Cephalopods  commenced  in  the 
Middle  Devonian.  Hitherto,  the  partitions  or  septa  in  the 
shells,  straight  or  coiled,  were  flat  or  simply  concave;  but 
in  the  new  genus  Goniatites  the  margin  of  the  plate  has  one 
or  more  deep  flexures,  one  of  the  flexures  or  pockets  being  at 
the  middle  of  the  back  of  the  shell.  The  name  is  from  the 
Greek  yow,  knee  or.  angle,  fig.  266  (page  236)  represents 
one  of  the  species,  and  Fig.  266  a  shows  some  of  the  flexures 
along  the  back  of  the  shell. 

Among  Articulates  there  were  Worms  and  Crustaceans,  as 
in  earlier  time,  and  the  most  common  Crustaceans  were  Trilo- 
bites.  Besides  these  there  were  the  first  of  Insects,  the  wings 
of  some  species  having  been  reported  from  the  Devonian  of 
New  Brunswick. 

Figs.  256-260. 


RADIATES,  —  Pig.  256,  Zaphrentis  Rafinesquii ;  257,  257  a,  Cyathophyllum  rugosum  : 
258,  Syringopora  Maclurii ;  25(J,  Aulopora  cornuta  ;  260,  Favorites  Goldfussi ;  all  of  the 
Corniferous  period. 

1,  Radiates.  —  Fig.  256,  one  of  the  Cyathophylloid  corals, 
Zaphrentis  Rafinesquii ;  Fig.  257,  another,  Cyathophyllum  ru- 
gosum, both  from  the  Falls  of  the  Ohio,  and  the  latter  form- 
ing very  large  masses.  Fig.  257  a  is  a  top  view  of  the  cells 
in  Fig.  257.  Fig.  260,  a  Favositcs  from  the  same  locality, 
showing  well  the  columnar  structure  characterizing  the  genus  ; 


236 


PALEOZOIC   TIME. 


the  species  F.  Goldfussi  occurs  both  in  America  and  Europe 
Figs.  258,  259  are  small  corals  from  Canada  West. 

2.  MoUusks.  — Figs.  .261   to   267,    Brachiopods   from   the 
Hamilton  beds;    Figs.  264,  265,   Lamellibranchs,  from   the 


2(31 


Figs.  261-267- 


MOLLUSKS  :  Fig.  261,  Atrypa  spinosa  ;  262,  Spirifer  mucronatus  ;  263,  Chonetes  setigera  * 
264,  Graminysia  bisuloata;  235,  Microdon  bellistriatus  ;  266,  263  a,  Goniatites  Marcel- 
lensis :  all  from  the  Hamilton  group.  —  ARTICULATES  :  Fig.  267,  Phacops  bufo,  from 
the  Hamilton  group. 

same ;  Fig.  266,  the  Cephalopod,  Goniatites  Marccllensis,  from 
the  same ;  Fig.  266  «,  a  view  of  the  back,  showing  the  flex- 
ures in  the  partitions,  this  species  having  but  one  flexure 
or  pocket. 

3.  Articulates..  —  Fig.  267,  the  Trilobite,  Phacops  bufo,  one 
of  the  common  species  of  the  Hamilton.  The  earliest  re- 
mains of  Insects  yet  discovered  have  been  found  in  beds 


DEVONIAN  AGE. 


237 


Fig-  268 


supposed  to  be  of  the  Hamilton  era,  at  St.  John's,  New 
Brunswick.  A  wing  of  a  gigantic  species  of  May-fly  is 
represented  in  Fig.  268. 

4,  Vertebrates.  —  The  fishes 
of  the  Devonian  belong  to 
three  orders  :  1.  the  Selachians, 
or  Sharks;  2.  the  Ganoids;  and 
3.  the  Placoderms.  The  Placo- 
dcrms  are  represented  in  Figs. 
269,  270.  The  name,  from  the 
Greek,  alludes  to  the  plates 
that  cover  the  body  much  like  those  of  a  turtle. 

Some  of  the  Ganoids  are  shown  in  Figs.  271-276.     The 

Figs.  269,  270. 


Platephemera  antiqua. 


VERTEBRATES.  —  Fig.  269,  Pterichthys  Milled  (X  §)  ;  270,  Coccosteus  decipiens  (X 


Ganoids  are  related  to  the  Gar-pike  of  some  modern  lakes 
and  rivers,  a  kind  of  fish  now  rarely  met  with.  They  have 
bony,  shining  scales,  and  to  this  the  name,  from  yavos,  shin- 
ing, alludes.  As  remarked  by  Agassiz,  they  have  several 


238 


PALEOZOIC  TIME. 


characters  that  aUy  them  to  Eeptiles ;  that  is,  (1)  they  have 
the  power  of  moving  the  head  at  the  articulation  between  the 
head  and  the  body,  the  articulation  being  made  by  means  of 
a  convex  and  concave  surface ;  (2)  the  air-bladder,  which  an- 
swers to  the  lung  of  higher  animals,  has  a  cellular  or  lung- 


Figs.  271-276. 
271 


GANOIDS.  —  Fig.  271,  Cephalaspis  Lyellii  (X  |) ;  272,  273,  scales  of  same  ;  274,  Holopty- 
chius  (X  £) ;  275,  scale  of  same;  276,  Dipterus  macrolepidotus  ( X  i);  276  a,  scale  ol 
same. 

like  structure,  thus  approximating  the  species  to  air-breathers ; 
(3)  the  teeth  have  in  general  a  structure  like  that  of  the  early 
Amphibians.  These  early  species  had  the  tail  vertebrated  (or 
heterocercal),  as  illustrated  in  Fig.  276.  Fig.  271  represents 
the  Cephalaspis,  having  a  flat  and  broad  plate-covered  head, 
with  rhombic  scales  over  the  body:  Fig.  273  shows  the 


DEVONIAN  AGE.  239 

form  of  some  of  the  scales.  Fig.  276  is  a  species  of  Dip- 
ierus,  covered  with  rhombic  scales,  put  on,  as  in  the  pre- 
ceding, much  as  tiles  are  arranged  on  a  roof:  Fig.  276  a 
is  one  of  the  scales,  natural  size.  Fig.  274  represents  another 
type  of  Ganoids,  having  the  scales  rounded  (as  shown  in  Fig. 
275)  and  set  on  more  like  shingles;  it  is  a  Holoptychius. 

A  gigantic  Placoderm  from  Ohio,  called  Dinichthys  by 
Newberry,  had  a  head  four  feet  wide,  with  dentate  lower  jaws 
twenty  inches  long.  It  was  related  to  the  Coccosteus,  and  also, 
according  to  its  describer,  to  the  modern  Lepidosiren. 

The  Selachians,  or  sharks,  belong  in  part  to  the  family  of 
Cestracionts  (pages  178,  179),  or  that  in  which  the  mouth  has 
a  pavement  of  broad  bony  pieces  for  grinding.  Others  had 
regular  teeth,  somewhat  like  those  of  ordinary  sharks ;  in  one 

Fig.  277- 


Fin-spine  of  a  Shark  (x  §). 


group  (the  Hybodonts)  the  teeth  had  prominent  points  (Figs. 
136, 137,  page  178),  and  in  another  they  were  of  a  broad  trian- 
gular shape.  There  were  species  as  large  as  the  largest  of  mod- 
ern time.  Fig.  277  represents  a  fin-spine  of  a  shark  two  thirds 
its  actual  size,  from  the  Corniferous  beds  of  New  York. 

4.  General  Observations. 

1.  Geography.  —  During  the  Silurian,  there  had  been  a  grad- 
ual gain  of  dry  land  on  the  north,  extending  the  Archaean 
continent  (page  199)  south  ward.  This  gain  continued  through 
the  Devonian,  so  that  the  formations  of  the  next  age,  the  Car- 
boniferous, extend  only  a  short  distance  north  of  the  southern 
boundary  of  New  York.  The  sea-shore  was  thus  being  set 
farther  and  farther  southward  with  the  progressing  periods. 

The  formations  have  their  greatest  thickness  along  the  Ap- 
palachian region,  as  in  the  Silurian  age.  And  both  this  fact 


240  PALEOZOIC  TIME. 

and  their  successions  lead  to  similar  general  conclusions  to 
those  stated  on  page  228. 

2.  Life.  —  The  great  feature  of  the  Devonian  age  is  the  oc- 
currence of  forests  of  Acrogens  and  Conifers  ;  of  Insects  and 
Myriapods,  among  terrestrial  Articulates ;  and  of  great  Sharks 
and  Gars  in  the  seas,  as  representatives  of  Vertebrates.  No 
Mosses  are  known  to  have  existed  as  intermediate  species 
between  Sea-weeds  and  the  earliest  Lycopods  and  Ferns. 

With  regard  to  Fishes,  the  earliest  species  belong  to  the 
two  high  groups  of  the  class,  —  the  Sharks  and  the  Ganoids ; 
the  Ganoids  being  a  type  that  is  partly  Eeptilian.  The  rocks 
have  afforded  no  evidence  of  any  links  between  the  Mollusk, 
Worm,  or  Trilobite  and  these  fishes. 

III.  CARBONIFEROUS  AGE,  or  AGE  OF  COAL 

PLANTS. 

I.  General  Characteristics:  Subdivisions. 

The  Carboniferous  age  was  remarkable,  in  general,  for  — 

1.  A  low  elevation  of  the  continents  above  the  sea-level 
through  long  eras  alternating  with  small  submergences  of  the 
same. 

2.  Extensive  marshy  or  fresh-water  areas  over  large  por- 
tions of  these  low  continents. 

3.  Luxuriant  vegetation,  covering  the  land  with  forests  and 
jungles. 

4.  Scorpions,  true    Spiders,  Centipedes,   Insects,  over   the 
land,  and  Amphibians  and  other  Reptiles  over  the  marshes 
and  in  the  seas. 

But,  while  having  these  as  its  main  characteristics,  it  was 
not  an  age  of  continued  verdure.  There  was,  first,  a  long 
period  —  the  Subcarboniferous  —  in  which  the  land  was 
largely  beneath  the  sea ;  for  limestone,  full  of  marine  fossils, 
is  the  prevailing  rock,  and  there  are  but  few,  and  mostly  thin 
coal-beds  in  the  sandstones  and  shales.  This  period  was  fol- 
lowed by  the  Carboniferous,  or  that  of  the  true  Coal-measures. 


CARBONIFEROUS   AGE.  241 

Yet  even  in  this  middle  period  of  the  age  there  were  alterna- 
tions of  submerged  with  emerged  continents,  long  eras  of  dry 
and  marshy  lands  luxuriantly  overgrown  with  shrubbery  and 
forest- trees  intervening  between  other  long  eras  of  great  bar- 
ren continental  seas.  Then  there  was  a  closing  period,  —  the 
Permian,  —  in  which  the  ocean  prevailed  again,  though  with 
contracted  limits ;  for  the  rocks  are  mainly  of  marine  origin. 

The  Carboniferous  period  and  age  were  so  named  from  the 
fact  that  the  great  coal-beds  of  the  world  originated  mainly 
during  their  progress.  The  term  Permian  was  given  to  the 
rocks  of  the  third  period  by  Murchison,  De  Verneuil,  and 
Keyserling,  from  a  region  of  Permian  rocks  in  Russia,  the  an- 
cient kingdom  of  Permia,  now  divided  into  the  governments 
of  Perm,  Viatka,  Kasan,  Orenberg,  etc. 

2.  Distribution  of  Carboniferous  Rocks. 

The  Carboniferous  areas  on  the  map  of  the  United  States, 
page  153,  are  the  dark  areas  ;  the  black  cross-lined  with  white 
being  the  Subcarboniferous ;  the  pure  black,  the  Carboniferous  ; 
the  black  dotted  with  white,  the  Permian.  The  last  occur 
only  west  of  the  Mississippi. 

The  following  are  the  positions  of  the  several  great  coal 
areas  in  North  America  :  — 

1.  EASTERN  BORDER  REGION.  —  1.  The  Rhode  Island  area, 
extending  from  Newport   in   Rhode  Island  northward  into 
Massachusetts. 

2.  The  Nova  Scotia  and  New  Brunswick  area. 

II.  ALLEGHANY  and  INTERIOR  REGIONS.  —  1.  The  great  Al- 
legliany  area,  extending  from  the  southern  borders  of  New 
York  and  Ohio  southwestward  to  Alabama,  covering  the 
larger  part  of  Pennsylvania,  half  of  Ohio,  part  of  Kentucky 
and  Tennessee,  and  a  portion  of  Alabama.  To  the  northeast, 
in  Pennsylvania,  this  coal-field  is  much  broken  into  patches,, 
as  shown  in  the  accompanying  map  of  a  part  of  the  State,  the 
black  areas  being  those  of  the  coal-district. 

2.  The  Michigan  area,  covering  the  central  part  of  the 
State  ^f  Michigan. 


242 


PALEOZOIC   TIME. 


3.  The  Illinois  or  Eastern  Interior  area,  covering  much  of 
Illinois,  and  part  of  Indiana  and  Kentucky.  ' 

4.  The  Missouri,  or  Western  Interior,  covering  part  of  Iowa, 
Minnesota,  Missouri,  Kansas,  Arkansas,  and  Northern  Texas. 


5.  Besides  these,  there  is  a  barren  Carboniferous  region 
about  the  slopes  and  summits  of  the  Eocky  Mountains,  as 
around  the  Great  Salt  Lake  in  Utah,  and  also  in  California, — 
the  workable  coal-beds  of  the  Rocky  Mountain  region  being 
Cretaceous  or  Tertiary. 


CARBONIFEROUS  AGE.  243 

III.  ARCTIC  KEGION.  —  On  Melville  Island,  and  other  isl- 
ands between  Grinnell  Land  and  Banks  Land,  mostly  north 
of  latitude  70°,  and  on  Spitzbergen  and  Bear  Island  north  of 
Siberia. 

The  areas  of  the  coal-measures  in  North  America  have  been 
estimated  as  follows : 

1.  Rhode  Island 500  square  miles. 

2.  Nova  Scotia  and  New  Brunswick     .  18,000        "        " 

3.  Alleghany 60,000         "         " 

4.  Michigan 5,000 

5.  Illinois  and  Missouri     ....  120,000         "        " 

But  of  these,  the  workable  portion  probably  does  not  exceed 
120,000  square  miles. 

Carboniferous  strata  occur  also  in  Great  Britain  and  various 
parts  of  Europe.  The  beds  in  England  are  distributed  over 
an  area  between  South  Wales  on  the  west  and  the  Newcastle 
basin  on  the  northeast  coast  (as  shown  by  the  black  areas  on 
the  following  map),  the  most  important  for  coal  being  the 
South  Wales  region;  the  Lancashire  district,  bordering  on 
Manchester  and  Liverpool ;  the  Yorkshire,  about  Leeds  and 
Sheffield ;  and  the  Newcastle.  In  South  Wales  the  thickness 
of  the  coal-measures  is  7,000  to  12,000  feet,  with  more  than 
100  coal-beds,  70  of  which  are  worked. 

Scotland  has  some  small  areas  between  the  Grampian 
range  on  the  north  and  the  Lammermuirs  on  the  south ;  and 
Ireland,  several  coal-regions  of  large  extent,  as  at  Ulster,  Con- 
naught,  Leinster  (Kilkenny)  and  Munster. 

The  coal-fields  of  Europe  which  are  most  worked  are  the 
Belgian,  bordering  on  and  passing  into  France.  Germany 
contains  only  small  coal-bearing  areas ;  and  Russia  in  Europe 
still  less,  although  the  Subcarboniferous  and  Permian  rocks 
cover  large  portions  of  the  surface. 

The  area  of  the  coal-measures  in  Great  Britain  and  Ireland 
is  about  12,000  square  miles;  in  Spain,  4,000;  in  France, 
2,000 ;  Belgium,  518. 

Valuable  coal-beds  are  not  found  in  any  rocks  older  than 


244  PALEOZOIC  TIME. 

those  of  the  Carboniferous  age,  although  black  carbonaceous 
shales  are  not  uncommon  even  in  the  Lower  Silurian.  They 
occur,  however,  in  different  Mesozoic  formations,  and  also 


Fig   279 


Fig.  279,  Geological  Map  of  England.  The  areas  lined  horizontally  and  numbered  1  are 
Silurian.  Those  lined  vertically  (2),  Devonian.  Those  cross-lined  (3),  Subcarboniferous. 
Carboniferous  (4),  black.  Permian  (5).  Those  lined  obliquely  from  right  to  left,  Triassic 
(6),  Lias  (7  a),  Oolite  (7  ft),  Wealden  (8),  Cretaceous  (9).  Those  lined  obliquely  from  left  to 
right  (10,  11),  Tertiary.  A  is  London,  B,  Liverpool,  C,  Manchester,  D,  Newcastle. 


CARBONIFEROUS  AGE.  245 

occasionally  in  the  Cenozoic,  but  not  of  the  extent  which 
they  have  in  the  Carboniferous  formations. 

3.  Kinds  of  Rocks. 

1.  Subcarboniferous  Period.  —  The  Subcarboniferous  strata 
in  the  Interior  Continental  region  are  mainly  limestone ;  and, 
as  the  limestone  abounds  in  many  places  in  Crinoidal  re- 
mains, the  rock  is  often  called  the  Crinoidal  limestone.     In 
the  Appalachian  region,  in  Middle  and  Southern  Virginia,  the 
rock  is  also  limestone,  and  has  great  thickness ;  but  in  North- 
ern Virginia  and  Pennsylvania  it  is  mostly  a  sandstone  or 
conglomerate  overlaid  by  a  shaly  or  clayey  sandstone  and 
marlytes  of  reddish  and  other  colors,  —  the  whole  having  a 
maximum  thickness  of  5,000  to  6,000  feet.     In  the  Eastern 
border  region,  in  Nova  Scotia,  the  rocks  are  mostly  reddish 
sandstone  and  marlyte,  with  some  limestone,  —  the  estimated 
thickness  6,000  feet. 

The  prevailing  rock  in  Great  Britain  and  Europe  is  a  lime- 
stone, called  there  the  Mountain  limestone. 

2.  Carboniferous  Period.  —  7.  Rocks  of  the  Coal-formation.  - 
The  rocks  of  the  Carboniferous  period  —  that  is,  those  of  the 
Coal-measures  —  are    sandstones,  shales,  conglomerates,  and 
occasionally  limestones ;  and  they  are  so  similar  to  the  rocks 
#f  the  Devonian  and  Silurian  ages  that  they  cannot  be  distin- 
guished except  by  the  fossils.     They  occur  in  various  alter- 
nations, with  an  occasional  bed  of  coal  between  them.     The 
coal-beds,  taken  together,  make  up  not  more  than  one  fiftieth 
of  the  whole  thickness ;  that  is,  there  are  50  feet  or  more  of 
barren  rock  to  1  foot  of  coal.     The  maximum  thickness  in 
Pennsylvania  is  4,000  feet ;  in  Nova  Scotia,  13,000  feet. 

The  following  is  an  example  of  the  alternations  :  — 

1.  Sandstone  and  conglomerate  beds 120    feet. 

2.  COAL         .         .         .        .         .        .    '      ,         .        .  6      " 

3.  Fine-grained  shaly  sandstone 50      " 

4.  Siliceous  iron-ore          .         .         .         .         .         .         .  1^    " 

5.  Argillaceous  sandstone    ..........       75      " 


246  PALEOZOIC  TIME. 

6.  COAL,  upper  4  feet  shale,  with  fossil  plants,  and  below 

a  thin  clayey  layer 7  feet 

7.  Sandstone 80  " 

8.  Iron-Ore 1  " 

9.  Argillaceous  shale 80  " 

10.  LIMESTONE  (oolitic),  containing  Producti,  Crinoids,  etc.  11  " 

11.  Iron-Ore,  with  many  fossil  shells     .....  3  " 

12.  Coarse  sandstone,  containing  trunks  of  trees        .         .  25  " 

13.  COAL,  lying  on  1  foot  slaty  shale  with  fossil  plants       .  5  " 

14.  Coarse  sandstone         .         .         .         .         .        .         .  12  " 

The  limestone  strata  are  more  numerous  and  extensive  in 
the  Interior  Continental  region  than  in  the  Appalachian; 
west  of  the  States  of  Missouri  and  Kansas  limestone  is  the 
prevailing  rock. 

Beds  of  argillaceous  iron-ore  or  clay-ironstone  are  very  com- 
mon in  coal-districts,  so  that  the  same  region  affords  ore  and 
the  coal  for  smelting  it.  Some  of  the  largest  iron-works  in 
the  world,  on  both  sides  of  the  Atlantic,  occur  in  coal-dis- 
tricts. The  ore  is  usually  the  carbonate  of  iron,  impure  from 
mixture  with  some  earth  or  clay. 

The  coal-beds  often  rest  on  a  bed  of  grayish  or  bluish  clay, 
called  the  under-day,  which  is  filled  with  the  roots  or  under- 
water stems  of  plants.  When  this  under-clay  is  absent,  the 
rock  below  is  usually  a  sandstone  or  shale.  Above  the  coal- 
bed  the  rock  may  be  sandstone,  shale,  conglomerate,  or  even 
limestone ;  often  the  layer  next  above,  especially  if  shaly,  is 
filled  with  fossil  leaves  and  stems.  In  some  cases,  trunks  of 
old  trees  rise  from  the  coal  and  extend  up  through  overlying 
beds,  as  in  the  annexed  figure,  by  Dawson,  from  the  Nova 
Scotia  Coal-measures.  Occasionally,  as  in  Ohio  and  Penn- 
sylvania, logs  50  to  60  feet  long  lie  scattered  through  the 
sandstone  beds,  looking  as  if  a  forest  had  been  swept  off 
from  the  land  into  the  sea. 

2.  Coal-Beds.  —  The  coal-beds  vary  in  thickness  from  a 
fraction  of  an  inch  to  30  or  40  feet,  but  seldom  exceed  8  feet, 
and  are  generally  much  thinner :  8  to  10  feet  is  the  thickness 
of  the  principal  bed  at  Pittsburg,  Pa. ;  29  J  feet,  that  of  the 


CARBONIFEROUS  AGE.  247 

"  Mammoth  Vein  "  at  Wilkesbarre,  Pa. ;  37J  feet,  that  of  one 
of  the  two  great  beds  at  Pictou  in  Nova  Scotia.  In  these 
thick  beds,  and  often  also  in  the  thin  ones,  there  are  some  in- 
tervening beds  of  shale,  or  of  very  impure  coal,  so  that  the 


whole  is  not  fit  for  burning. 


Fig    280. 


Section  of  a  portion  of  the  Coal-measures  at  the  Joggins,  Nova  Scotia,  having  erect  stumps, 
and  also  "rootlets  "  in  the  under-clays. 

The  coal  varies  in  kind,  as  explained  on  page  18,  that  burn^ 
ing  with  little  flame  being  called  anthracite,  and  that  with 
a  bright  yellow  flame  bituminous  coal.  When  only  12  or  15 
per  cent  of  volatilizable  substances  are  present,  it  is  often 
called  semi-bituminous  coal.  In  Pennsylvania  the  coal  of 
the  Pottsville,  Lehigh,  and  Wilkesbarre  regions  is  anthracite  : 
that  of  Pittsburg  and  the  West,  bituminous  coal ;  and  that  of 
part  of  the  intermediate  district,  semi-bituminous,  as  desig- 
nated on  the  map,  page  242. 

The  coal  also  varies  as  to  the  impurities  present.  All  of 
it  contains  more  or  less  of  earthy  material,  and  this  earthy 
material  constitutes  the  ashes  and  slag  of  a  coal-fire.  Ordi- 
nary good  anthracite  contains  7  to  12  pounds  of  impurities 
in  a  hundred  pounds  of  coal,  and  the  best  bituminous  coals  3 
to  7.  In  some  coal-beds  there  is  much  sulphide  of  iron  or 
pyrite  (a  compound  of  sulphur  and  iron),  and  the  coal  is  then 
unfit  for  use.  It  is  seldom  that  the  sulphide  is  altogether 
absent ;  it  is  the  chief  source  of  the  sulphur  gases  that  are 
perceived  in  the  smoke  or  gas  from  a  coal-fire. 


248  PALEOZOIC  TIME. 

Mineral  coal,  although  it  seldom  breaks  into  plates  unless 
quite  impure,  still  consists  of  thin  layers.  Even  the  hardest 
anthracite  is  delicately  banded,  as  seen  on  a  surface  of  frac- 
ture when  it  is  held  up  to  the  light.  This  structure  is  absent 
in  the  variety  called  Cannel  coal,  which  is  a  bituminous  coal, 
very  compact  in  texture,  feeble  in  lustre,  and  smooth  in  frac- 
ture. 

3.  Mineral  Oil.  —  Besides  mineral  coal,  the  rocks  sometimes 
afford,  when  heated,  liquids  consisting  of  carbon  and  hydro- 
gen, called  ordinarily  petroleum  or  mineral  oil,  and  bitumen  ; 
when  purified  for  burning  it  becomes  kerosene.     Oil-wells  are 
largely  worked   at   Titusville,  in   Pennsylvania,  and   about 
Mecca,  in  Trumbull  County,  Ohio,  regions  of  Subcarbonif- 
erous  rocks.     The  wells  are  borings  into  an  inferior  part  of 
the  Subcarboniferous  formation,  or  into  the  upper  part  of  the 
Devonian.     When  a  boring  reaches  the  oil-level,  the  oil  rises 
to  the  surface,  and  sometimes  issues  in  a  jet.    The  oil  is  there- 
fore in  subterranean  cavities,  and  under  pressure.     It  has 
probably  reached  those  cavities  from  some  subjacent  region 
of  oil-yielding  shales  or  limestones.     These  shales,  like  the 
Erie  shale  of  the  Chemung  period,  in  Ohio,  or  the  black  shale 
of  the  Genesee  epoch  of  the  Hamilton  period,  or  the  Utica 
shale  of  the  Lower  Silurian,  are  black  from  the  carbonaceous 
material  penetrating  them ;  and  although  they  do  not  contain 
any  oil  (for  the  solvents  of  it  take  up  none  from  them,  or  but 
traces),  they  contain   compounds   of  carbon   and   hydrogen 
(probably  oxygenated)  which,  when  the  shale  is  heated,  yield 
the  oil  or  liquid  carbo-hydrogen.     Thus  the  shales  are  oil- 
yielding,  though  not  oil-containing.     The  regions  of  wells  are 
mostly  along  lines  of  axes  of  disturbance ;  and  probably  the 
heat  developed  by  the  movement  of  disturbance  caused  the 
production  of  the  oil  and  its  rising  into  any  opened  spaces 
above.     Petroleum  is  a  result  of  the  decomposition  of  vege- 
table or  animal  substances. 

4.  Salt  or  Salines.  —  The   Subcarboniferous   formation   in 
Michigan,  in  the  Saginaw  Valley,  and  in  the  adjoining  region, 


CARBONIFEROUS  AGE.  249 

affords  extensive  salines,  and  many  wells  have  been  opened 
by  boring.  The  beds  affording  the  saline  waters  consist  of 
clayey  beds  or  marlytes,  shale,  and  magnesian  limestone,  and 
abound  also  in  gypsum,  thus  resembling  those  of  the  Salina 
period  in  New  York  (page  220). 

3.  Permian  period,  —  The  upper  part  of  the  Carboniferous 
formation  (mostly  barren  of  coal)  in  Pennsylvania  and  Vir- 
ginia has  been  shown  by  its  plants,  and  of  Illinois,  Kansas,  and 
Texas,  by  its  fossil  reptiles  or  mollusks,  to  be  Permian.  Per- 
mian strata  occur  also  in  the  Pocky-Mountain  region.  The 
rocks  are  mostly  reddish  and  gray  sandstones  and  shales,  with 
some  impure  limestone.  Similar  rocks  uccur  in  Great  Britain 
in  the  vicinity  of  several  of  the  coal-regions,  and  also  in 
Germany  and  Russia. 

4.    Life. 

1.    Plants. 

The  plants  of  the  forests,  jungles,  and  floating  islands  of 
the  Carboniferous  age,  thus  far  made  known,  number  about 
300  species.  Among  the  fossils  there  are  none  that  afford 
satisfactory  evidence  of  the  presence  of  either  Angiosperms 
3T  Palms  (page  189);  for  no  net- veined  leaves,  allied  in  char- 
acter to  those  of  the  Oak,  Maple,  Willow,  Hose,  etc.,  have  been 
found  among  them ;  and  no  palm-leaves  or  palm-wood.  More- 
over, the  plains  were  without  grass,  and  the  swamps  and 
woods  without  moss.  At  the  present  day  Angiosperms, 
along  with  Conifers  or  the  Pine  family,  make  up  the  great 
bulk  of  our  shrubs  and  trees  ;  Palms  abound  in  all  tropical 
countries ;  grass  covers  all  exposed  slopes  where  the  climate 
is  not  too  arid ;  and  mosses  are  the  principal  vegetation  of 
most  open  marshes. 

The  view  in  Fig.  281  gives  some  idea  of  the  Carboniferous 
vegetation  over  the  plains  and  marshes  of  the  era. 

The  Carboniferous  species,  like  their  predecessors  in  the 
Devonian  age,  belonged  to  the  following  groups  :  — 


250 


PALEOZOIC  TIME. 
Fig.  281. 


jr.  ,,    v»    •'  ''•     f      -v 

f         or  Ti-ic          \ 
VNlVB?tr»ITY    s 
CARBONIFEROUS  AGE. 


251 


I.  Cryptogams,  or  Flowerless  Plants,  Order  of 
Acrogens. 

1,  Fern  Tribe.  —  Ferns  were  very  abundant,  a  large  part  of 
the  fossil  plants  of  a  coal-region  being  their  delicate  fronds 
(usually  called  leaves).  A  portion  of  a  fossil  fern  is  repre- 


Figs.  282-287- 


Fig.  282,  Lepidodendron  aculeatum  ;  283,  Sigillaria  oculata  ;  284,  Stigmaria  ficoides ;  285, 
Sphenopteris  Gravenhorstii  ;  28G,  Culamites  cannseformis ;  287,  Trigoriocarpus  tricuspi- 
datus. 

sented  in  Fig.  285.     Besides  small  species,  like  the  common 
kinds  of  the  present  day,  there  were  Tree-ferns,  species  that 


252  PALEOZOIC  TIME. 

had  a  trunk,  perhaps  20  or  30  feet  high,  and  which  bore  at 
top  a  radiating  tuft  of  the  very  large  leaf-like  fronds,  resem- 
bling the  modern  tree-fern  of  the  tropics.  One  of  the  tree- 
ferns  of  the  Pacific  is  represented  in  Fig.  281,  near  the  middle 
of  the  view,  and  smaller  ferns  in  front  of  it  below.  Tree- 
ferns,  however,  were  not  very  common  in  the  Carboniferous 
forests.  The  scars  in  fossil  or  recent  tree-ferns  are  many 
times  larger  than  those  of  Lepidodendrids,  and  the  fossils  may 
be  thus  distinguished. 

2,  Lycopodium  Tribe,  —  1.  The  Lepidodendrids  appear  tc 
have  been  among  the  most  abundant  of  Carboniferous  forest- 
trees,  especially  in  the  earlier  half  of  the  Carboniferous  Age,  or 
to  the  middle  of  the  Coal  Period.  They  probably  covered  both 
the  marshes  and  the  drier  plains  and  hills.  Some  of  the  old 
logs  now  preserved  in  the  strata  are  50  to  60  feet  in  length, 
strikingly  contrasting  with  the  little  Ground-Pines  of  modern 
times;  and  the  pine-like  leaves  were  occasionally  a  foot  or 
more  long.  The  taller  tree  to  the  left,  on  page  250,  is  a  Lepi- 
dodendron.  Fig.  282  shows  the  surface-markings  of  one  of 
the  species,  natural  size. 

2.  Sigillarids.  —  The  Sigillarice  were  a  very  marked  feature 
of  the  great  jungles  and  damp  forests  of  the  Coal  period. 
They  grew  to  a  height  sometimes  of  30  to  60  feet ;  but  the 
trunks  were  seldom  branched,  and  must   have  had  a  stiff, 
clumsy  aspect,  although  covered   above  with   long,  slender, 
rush-like  leaves.     Fig.  283  represents  a  common  species,  ex- 
hibiting the  usual  arrangement  of  the  scars  in  vertical  lines, 
and  also  indicating,  by  the  difference  in  the  scars  of  the  right 
row  from  those  of  the  others,  their  difference  of  form  on  the 
outer  surface  of  the  tree  and  beneath  the  surface. 

3.  Stigmarice.  —  The  fossil  Stigmaricc  are  stout  stems,  gen- 
erally 2  to  3  or  more  inches  thick,  having  over  the  surface 
distinct  rounded  punctures  or  depressions.     Fig.  284  is  a  por- 
tion of  the  extremity  of  a  stem,  showing  the  rounded  depres- 
sions and  also  the  leaf-like  appendages  occasionally  observed. 
The  stems  or  branches  are  a  little  irregular  in  form,  and  spar- 


CARBONIFEROUS  AGE.  253 

ingly  branched.  They  have  been  found  spreading,  like  roots, 
from  the  base  of  the  trunk  of  a  Sigillaria,  and  sometimes  also 
from  that  of  a  Lepidodendron ;  and  they  are  hence  regarded 
either  as  the  roots  or  subaqueous  stems  of  these  trees.  They 
are  an  exceedingly  common  fossil,  especially  in  the  under- 
clays  of  the  Coal-measures  (page  246). 

3.  Equisetum  Tribe,  —  Fig.  286  represents  a  portion  of  one 
of  the  tree-rushes,  or  Calamites,  of  the  Equisetum  or  Horse- 
tail tribe.  The  specimens  were  very  abundant  in  the  great 
marshes,  through  the  whole  of  the  Carboniferous  Age.  Some 
of  them  were  20  feet  or  more  high  and  10  or  12  inches  in 
diameter. 

Besides  these  Cryptogams  there  were  also  Fungi;  but,  as 
already  stated,  no  remains  of  Mosses  from  the  rocks  of  the 
age  are  known. 

In  the  ideal  view  of  a  Carboniferous  landscape,  Fig.  281, 
page  250,  the  broken  trunk  to  the  right  is  a  Sigillaria.  The 
landscape,  to  be  quite  true  to  nature,  should  have  been  made 
up  largely  of  Sigillaria^,  Calamites,  and  Lcpidodcndra,  with 
few  tree-ferns.  The  Stigmariae  should  have  been  mostly  con- 
cealed beneath  the  water  or  soil,  or  in  the  submerged  mass  of 
the  floating  islands. 

II.  Phenogams,  or  Flowering  Plants,  Order  of 
Gymnosperms. 

1.  Conifers.  —  Trunks  of  trees,  Coniferous  in  character,  and 
related  especially  to  the  Araucanian  pines,  are  not  uncommon. 

2.  Fruits.  —  Besides  the  leaves,  stems,  and  trunks  already 
alluded  to,  there  are  various  nut-like  fruits  found  in  the  Car- 
boniferous strata.     One  is  represented  in  Fig.  287  (page  251), 
the  figure  to  the  left  being  that  of  the  shell,  and  the  other 
that  of  the  nut  which  it  contained.     Some  of  them  are  two 
inches  in  length.     The  most  of  them  were  probably  the  fruit 
of  Conifers. 

It  is  seen  from  the  above  that  — 

1.  The  vegetation  of  the  Carboniferous  age  consisted  very 
largely  of  Cryptogams,  or  flowerless  plants. 


254  PALEOZOIC  TIME. 

2.  The  flowering  plants,  or  Phenogams,  associated  with  the 
flowerless  vegetation,  were   of  the   order   of  Gymnosperms, 
whose  flowers  are  imperfect  and  inconspicuous. 

3.  While,  therefore,  there  was  abundant  and  beautiful  fo- 
liage (for  no  foliage  exceeds  in  beauty  that  of  Ferns),  the 
vegetation  was  nearly  flowerless. 

4.  The  characteristic  Cryptogams  were   not  only  of  the 
highest  group  of  that  division  of  plants,  but  in  general  they 
exceeded  in  size  and  perfection  the  species  of  the  present  day, 
many  being  forest-trees. 

2.   Animals. 

1.  Radiates.  —  Among  Piadiates,  species  of  Crinoids  were 
especially  numerous  in  the  Subcarboniferous  period.     Figs. 
288,  289,  290  represent  some  of  the  species.     The  radiating 
arms  are  perfect  in  Fig.  288,  but  wanting  in  289.     Fig.  290 
is  a  species  of  the  genus  Pentremites  (named  from  the  Greek 
Tre^re,  Jive,  alluding  to  the  five-sided  form  of  the  fossil).     The 
Pentremites  had  a  stem  made  of  calcareous  disks,  like  other 
Crinoids,  but  no  long  radiating  arms  at  top. 

Fig.  291  presents  an  upper  view  of  a  very  common  Coral 
of  the  same  period :  it  has  a  columnar  appearance  in  a  side 
view. 

2.  Mollusks.  —  The  tribe  of  Bryozoans  contained  the  singu- 
lar screw-shaped  (or  auger-shaped)  Coral  shown  in  Fig.  292, 
and  named  Archimedes  (referring  to  Archimedes'  screw).     It 
is  made  up  of  minute  cells  that  open  over  the  lower  surface ; 
each  of  the  cells,  when  alive,  contained  a  minute  Bryozoum 
(page  183).     These  fossils  are  common  in  some  of  the  Subcar- 
boniferous limestone  strata. 

Brachiopods  were  the  most  abundant  of  Mollusks  through 
the  Carboniferous  age,  and  especially  species  of  the  genera 
Spirifer  and  Productus.  Figs.  293  to  296  are  of  species  from 
the  American  Coal-measures:  Fig.  295,  a  Spirifer ;  Fig.  294, 
a  Productus;  Fig.  293,  a  Chonetes ;  Fig.  296,  an  Athyris,  oc- 
curring also  in  Europe.  Fig.  297  represents  one  of  the  Gas- 


CARBONIFEROUS  AGE. 


255 


teropods  of  the  Coal-measures.     Fig.  298  is  a  Pupa,  the  earli- 
est yet  found  of  land-snails :  it  is  from  the  Coal-measures  of 


Figs.  288-298. 


291 


RADIATES  :  Fig.  288,  Zeacrinus  elegans  ;  2SO,  Actinocrinus  proboscidians  ;  290,  Peutre- 
inites  pyriforniis  ;  291,  Lithostrotion  Canadense.  —  MOLLUSKS  :  Fig.  292,  Archimedes 
reversa;  293,  Chonetes  mesoloba;  294,  Produetus  Nebrascensis  :  295,  Spirifer  cameratus ; 
296,  Athyris  subtilita ;  297,  Pleurotomaria  tabulata  ;  298,  Pupa  vetusta. 

Nova  Scotia ;  others  have  been  found  in  Illinois.  The  order 
of  Cephalopods  contained  but  few  and  small  species  of  the 
old  tribe  of  Orthocerata,  but  many  of  the  Ammonite-like  Go- 
niatitcs. 


256* 


PALEOZOIC   TIME. 


3.  Articulates,  —  Among  Articulates,  Crustaceans  appeared 
under  a  new  form,  much  like  that  of  modern  shrimps,  and 
Trilobites  were  of  rare  occurrence. 

Figs.  299-301. 


CPIDERS:    Fig.  "299,  Arthrolycosa  antiquus  ;  30<\  Eoscorpius  carbonarius.  —  INSECT : 
Fiy.  301,  Miamia  Bronsoui. 

Besides  Insects  (Fig.  301),  there  were  also  Myriapods,  true* 
Spiders  (Fig.  299),  and  Scorpions  (Fig.  300) ;  the  figures  ^are 
of  Illinois  species.  The  Insects  include  May-flies  (Neurop- 
ters),  Locusts  and  Cockroaches  (or  Orthopterous  insects),  and 
Beetles  (or  Coleopters). 

4.  Vertebrates.  —  Fishes  were  numerous,  both  of  the  orders 
of  Ganoids  and  Selachians.  All  the  Ganoids  were  of  the  art- 


CARBONIFEROUS  AGE 


257 


cient  type,  having  the  tail  vertebrated  (or  heterocercal),  as 
in  Fig.  302,  representing  a  Permian  species  of  Palceoniscus. 
Many  of  the  Selachians,  or  Sharks,  were  of  great  size,  as 
shown  by  the  fin-spines.  Fig.  303  represents  a  small  portion 
of  one  of  these  spines,  natural  size,  from  the  Subcarboniferous 
beds  of  Europe.  One  of  the  largest  specimens  of  the  same 
species  when  entire  must  have  been  18  inches  long. 


Figs.  302,  303. 


Fig.  302,  Palseoniscus  Freieslebeni  (x£);  303,  Part  of  a  spine  of  Ctenacanthus  major. 


Amphibian  Reptiles  occur  through  the  age.  They  are  called 
Ldbyrinlhodonts,  because  the  teeth,  like  those  of  the  Ganoids, 
are  labyrinthine  in  the  arrangement  of  the  dentine.  The  ear- 
liest traces  are  tracks  found  in  the  Subcarboniferous  beds  at 
Pottsville,  Pa.  (Fig.  304);  they  are  about  four  inches  broad, 
those  of  the  fore-feet,  as  described  by  Dr.  Lea,  5-fingered,  and 
those  of  the  hind-feet  4-fingered.  Fig.  305  represents  a  skele- 
ton of  another  species  from  the  Ohio  Coal-measures,  found  by 
Newberry.  Some  of  the  related  Amphibians  from  Ohio  are 
long,  like  snakes. 

17 


258 


PALEOZOIC  TIME. 


True  Reptiles  appear  to  have  been  represented  in  the  Coal 
period  by  swimming  species,  or  Enaliosaurs  ;  and,  in  the  Per- 


Figs.  304-306. 


304 


l-'ig.  304,  Tracks  of  Sauropus  primsevris  (x  £) ;  305,  Raniceps  Lyellii ;  306,  a,  Vertebra  o,' 
Eosaurus  Acadianus. 

mian  period,  by  higher  Crocodile-like  Reptiles  of  the  tribe  of 
Thecodonts.  The  Enaliosaurs  (or  sea-lizards,  as  the  word  sig- 
nifies) had  paddles  like  whales,  and  doubly  concave  vertebrae, 


CARBONIFEROUS  AGE.  259 

like  fishes.  (Figs.  361  and  365  represent  Mesozoic  species.) 
A  vertebra,  found  by  Marsh  in  Nova  Scotia,  and  referred  by 
him  to  the  Enaliosaurs,  is  represented  in  Fig.  306;  and  Fig. 
306  a,  a  transverse  section,  shows  the  biconcave  character. 
The  Thecodouts  also  had  the  fish-like  character  of  biconcave 
vertebrae.  They  had  the  teeth  in  sockets,  like  the  Crocodiles, 
and  hence  the  name  Thecodont. 

5.  General  Observations. 

1.  Formation  of  Coal,  and  origin  of  the  Coal-measures.  —  7. 

Origin  of  the  Coal.  —  The  vegetable  origin  of  coal  is  proved 
by  the  following  facts  :  — 

1.  Trunks  of  trees,  retaining  still  the  original  form  and 
part  of  the  structure  of  the  wood,  have  been  found  changed 
to  mineral  coal,  both  in  the  Carboniferous  strata  and  in  more 
modern  formations,  showing  that  the  change  may  and  does 
take  place. 

2.  Beds  of  peat,  a  result  of  vegetable  growth  and  accumu- 
lation, exist  in  modern  marshes ;  and  in  some  cases  they  are 
altered  below  to  an  imperfect  coal.     (See   page  75,  on   the 
formation  of  peat.) 

3.  Eemains  of  plants,  their  leaves,  branches,  and  stems  or 
trunks,  abound  in  the  Coal-measures ;  trunks  sometimes  ex- 
tend upward  from  a  coal-bed  into  and  through  some  of  the 
overlying  beds  of  rock ;  roots  or  stems  abound  in  the  under- 
clays. 

4.  The   hardest   anthracite   contains  throughout   its   mass 
vegetable  tissues.     Professor   Bailey  examined  with  a  high 
magnifying  power  several  pieces  of  anthracite  burnt  at  one 
end,  like  Fig.  307,  taking  fragments  from  the  junction  of  the 
white  and  black   portion,  and  detected   readily  the  tissues. 
Fig.  308  represents  the  ducts,  as  they  appeared  in  one  case 
under  his  microscope;  and  Fig.  309  part  of  the  same,  more 
magnified.     Fig.  310  shows  the  appearance  of  the  spores  of 
Lycopods  (Lepidodendrids)  much  magnified ;  they  are  com- 
mon in  coal. 


260 


PALEOZOIC   TIME. 


2.  Decomposition  of  Vegetable  Material.  —  The  Mineral  Coal  of 
the  Coal-measures  consists  (impurities  excluded)  of  77  to  97 
per  cent  of  carbon  along  with  2  to  6  of  hydrogen  and  2  to  15 
of  oxygen ;  and  woody  material,  whether  of  Conifers,  Ferns, 
Lycopods,  or  Equiseta,  consists  of  about  50  per  cent  of  car- 
bon, 6  of  hydrogen,  and  44  of  oxygen.  To  change  the  vege- 

Pigs.  307-309. 


309 


Fig.  310 


Vegetable  tissues  in  Anthracite. 

table  material  to  coal,  it  is  necessary  to  g^t  rid  of  part  of  the 
oxygen  and  hydrogen.     Vegetable  matter  decomposing  in  the 

open  air  —  like  wood  burnt 
in  an  open  fre  —  passes  into 
gaseous  combinations,  and  lit- 
tle or  no  carbon  is  left  behind. 
Both  the  oxygen  of  the  air 
and  that  of  the  wood  take  part 
in  the  combustion  or  decom- 
position. But  if  the  former 
is  more  or  less  excluded  by 
a  covering  of  earth  (as  of 
strata)  or  of  water  (as  in  a 
swamp),  the  combustion  is 
incomplete,  and  coal  may  re- 
sult, consisting  of  the  uncon- 

sumed  carbon  combined  with  some  hydrogen  and  oxygen. 
The  actual  loss,  by  weight,  in  the  transformation  into  bitu- 


Spores  and  part  of  a  Sporangium  in  bitumi- 
nous coal  of  Ohio  ( x  70). 


CARBONIFEROUS  AGE.  261 

ruinous  coal,  is  at  least  three  fifths  of  the  wood,  and  in  that  into 
anthracite,  three  fourths.  Adding  to  this  loss  that  from  com- 
pression, by  which  the  material  is  brought  to  the  density  of 
mineral  coal,  the  whole  redaction  in  bulk  is  not  less  than  to 
one  fifth  for  the  former,  and  to  one  eighth  for  the  latter.  In 
other  words,  it  would  take  5  feet  of  vegetable  matters  to  make 
1  of  bituminous  coal,  and  8  feet  to  make  1  of  anthracite. 

3.  Impurities  in  Coal.  —  The  coal  thus  formed  derived  some 
silica  and  other  earthy  ingredients  from  the  wood  itself,  and 
alumina  from  the  Lepidodendrids,  this  earth  existing  in  the 
ash  of  modern  Lycopods.     By  this  means  the  best  coal  re- 
ceived some  earthy  impurities,  while  the  poorer  coals  contain 
clay  or  earthy  material  carried  over  the  marshes  by  the  waters 
or  winds.     Sulphur  is  a  common  impurity ;  it  usually  occurs 
combined  with  iron,  forming  pyrite  or  sulphid  of  iron. 

4.  Accumulation  and  Formation  of  Coal-beds.  —  The  origin  of 
coal-beds   was,  then,  as    follows :  The   plants   of  the   great 
marshes  and  shallow  lakes  of  the  Coal  era,  the  latter  with 
their  floating  islands  of  vegetation,  continued  growing  for  a 
long  period,  dropping  annually  their  leaves,  and  from  time  to 
time  decaying  stems  or  branches,  until  a  thick  accumulation 
of  vegetable  remains  was  formed,  —  probably  5  feet  in  thick- 
ness for  a  one-foot  bed  of  bituminous  coal.     The  bed  of  ma- 
terial thus  prepared  over  the  vast  wet  areas  of  the  continent 
early  commenced  to  undergo  at  bottom  that  slow  decomposi- 
tion the  final  result  of  which  is  mineral  coal.     But,  as  the 
coal-beds  alternate  with  sandstones,  shales,  conglomerates,  and 
limestones,   the    long   period   of   verdure   was   followed    by 
another  of  overflowing  waters,  —  and  generally,  in  the  case 
of  the  region  of  the  Interior  basin  of  North  America,  oceanic 
waters,  as  the  fossils  prove,  —  which  carried  sands,  pebbles, 
or  earth,  over  the  old  marsh,  till  scores  or  hundreds  of  feet  in 
depth  of  such  deposits  had  been  made.     Thus  the  bed  of 
vegetable  material  was  buried ;  and  under  this  condition  the 
process  of  decomposition  and  change  to  mineral  coal  went 
forward  to  its  completion ;  it  had  the  smothering  influence  of 


262  PALEOZOIC  TIME. 

the  burial,  as  well  as  the  presence  of  water,  to  favor  the  pro- 
cess. 

5.  Climate  of  the  Age.  —  The  wide  distribution  of  the  coal 
regions  over  the  globe,  from  the  tropics  to  remote  Arctic 
lands,  and  the  general  similarity  of  the  vegetable  remains  in 
the  coal-beds  of  these  distant  zones,  prove  that  there  was  a 
general  uniformity  of  climate  over  the  globe  in  the  Carbon- 
iferous age,  or  at  least  that  the  climate  was  nowhere  colder 
than  warm-temperate.     Besides,  corals  and  shells  existed  dur- 
ing the  Subcarboniferous  period  in  Europe,  the  United  States, 
and  the  Arctic  within  20°  of  the  north  pole,  and  so  profusely 
as  to  form  thick  limestones  out  of  their  accumulations ;  and 
some  Arctic  species  are  identical  with  those  of  Europe  and 
America.     The  ocean's  waters,  even  in  the  far  north,  were, 
therefore,  warm  compared  with  those  of  the  modern  temper- 
ate zone,  and  probably  quite  as  warm  as  the  coral-reef  seas 
of  the  present  age,  which  lie  mostly  between  the  parallels  of 
28°  cither  side  of  the  equator. 

6.  Atmosphere.  —  The  atmosphere  was  especially  adapted  for 
the  age  in  other  respects.     It  contained  a  larger  amount  than 
now  of  carbonic-acid  gas,  —  the  gas  which  promotes  (if  not  in 
excess)  the  growth  of  vegetation.     Plants  derive  their  carbon 
mainly  from  the  carbonic  acid  of  the  atmosphere ;  and  hence 
the  mineral  coal  of  the  world  is  approximately  a  measure  of 
the  amount  of  carbonic  acid  the  atmosphere  in  the  Carbonif- 
erous era  lost.     The  growth  of  the  flora  of  tha,t  age  was  a 
means  of  purifying  the  atmosphere  so  as  to  fit  it  for  the  higher 
terrestrial  life  that  was  afterward  to  possess  the  world. 

Again,  the  atmosphere  was  more  moist  than  now.  This 
follows  from  the  greater  heat  of  the  climate  and  the  greater 
extent  as  well  as  higher  temperature  of  the  oceans.  The  con- 
tinents, although  larce  during  the  intervals  of  verdure  com- 

O  O  o 

pared  with  the  areas  above  the  ocean  in  the  Devonian  or  Si- 
lurian, were  still  small  and  the  land  low.  It  must,  therefore, 
have  been  an  era  of  prevailing  clouds  and  mists.  A  moist 
climate  would  not,  however,  have  been  universal,  since  even 


CAKBONIFEROUS  AGE.  263 

the  ocean  has  now  its  great  areas  of  drought  depending  on  the 
courses  of  the  winds.  America  is  now  the  moist  forest-conti- 
nent of  the  globe ;  and  tiie  great  extent  of  the  coal-fields  of 
its  northern  half  proves  that  it  bore  the  same  character  in  the 
Carboniferous  age. 

2.  Geography.  —  7.  Appalachian  and  Rocky  Mountains  not  made. 
—  On  page  240  it  is  stated  that  the  continents  in  this  age 
were  low,  with  few  mountains.  The  non-existence  of  the 
Appalachians  of  Pennsylvania  and  Virginia  is  proved  by  the 
fact  that  the  rocks  of  these  mountains  are  to  a  considerable 
extent  Carboniferous  rocks;  —  partly  marine  rocks,  indicat- 
ing that  the  sea  then  spread  over  the  region ;  partly  coal-beds, 
each  bed  evidence  that  a  great  fresh-water  marsh,  flat  as  all 
marshes  are,  for  a  long  while  occupied  the  region  of  the  pres- 
ent mountains. 

There  is  the  same  evidence  that  the  mass  of  the  Rocky 
Mountains  had  not  been  lifted;  for  marine  Carboniferous 
rocks  constitute  a  large  part  of  these  mountains,  many  beds 
containing  remains  of  the  life  of  the  Carboniferous  seas  that 
covered  that  part  of  North  America.  Only  islands,  or  archi- 
pelagoes of  islands,  made  by  some  Archaean  and  perhaps 
also  Paleozoic  ridges,  existed  in  the  midst  of  the  widespread 
western  waters. 

2.  Condition  in  the  Subcarboniferous  Period.  —  Through  the  first 
period  of  this  age  —  the  Subcarboniferous  —  the  continent 
was  almost  as  extensively  beneath  the  sea  as  in  the  Devonian 
age.  This,  again,  is  shown  by  the  nature  and  extent  of  the 
Subcarboniferous  rocks,  —  the  great  crinoidal  limestones. 
The  shallow  continental  seas  were  profusely  planted  with 
Crinoids  amid  clumps  of  Corals.  Brachiopods  were  here  and 
there  in  great  abundance,  many  lying  together  in  beds  as  oys- 
ters in  an  oyster-bed;  other  Mollusks,  both  Lamellibranchs 
and  Gasteropods,  were  also  numerous ;  Trilobites  were  few ; 
Goniatites  and  Nautili,  along  with  Ganoid  Fishes  and  Sharks, 
were  the  voracious  life  of  the  seas,  and  Amphibian  reptiles 
haunted  the  marshes. 


264  PALEOZOIC  TIME. 

3.  Transition  to  the  Carboniferous  Period.  —  Finally,  the  Sub- 
carboniferous  period  closed,  and  the  Carboniferous  opened. 
But  in  the  transition  from  the  period  of  submergence  to  that 
of   emergence,  required   to   bring   into   existence   the   great 
marshes,  a  widespread  bed  of  pebbles,  gravel,  and  sand  was 
accumulated  by  the  waves  dashing  rudely  over  the  surface  of 
the  rising  continent;  and  these  pebble-beds  make  the  Mill- 
stone grit  that  marks  the  commencement  of  the  Carboniferous 
period  in  a  large  part  of  Eastern  North  America,  especially 
along  the  Appalachian  region,  and  also  in  Europe.  ^ 

4.  Coal-plant  Areas  in  the  Carboniferous  Period.  —  Then  began 
the  epoch  of  the  Coal-measures. 

The  positions  of  the  great  coal  areas  of  North  America 
(see  map,  page  195)  are  the  positions,  beyond  question,  of  the 
great  marshes  and  shallow  fresh- water  lakes  of  the  period. 
But  it  is  probable  that  the  number  of  these  marshes  was  less 
than  that  of  the  coal  areas.  The  Appalachian,  Illinois,  Mis- 
souri, Arkansas,  and  Texas  fields  may  have  made  one  vast 
Interior  continental  marsh-region,  and  those  of  Ehode  Island, 
Nova  Scotia,  and  New  Brunswick  an  Eastern  border  marsh- 
region  connected  over  Massachusetts  Bay  and  the  Bay  of 
Fundy.  There  is  reason,  however,  for  believing  that  a  low 
area  of  dry  land  extending  from  the  region  of  Cincinnati  into 
Kentucky  (page  217)  divided  at  least  the  northern  portion 
of  the  Interior  marsh. 

The  Michigan  marsh-region  appears  also  to  have  had  its 
dry  margins,  instead  of  coalescing  with  the  Illinois  or  Ohio 
areas. 

It  is  not  to  be  inferred  that  the  marshes  alone  were  cov- 
ered with  verdure.  The  vegetation  probably  spread  over  all 
the  dry  land,  though  making  thick  deposits  of  vegetable  re- 
mains only  where  there  were  marshes  under  dense  jungles 
and  shallow  lakes  with  their  floating  islands. 

5.  Alternations  of  Condition :  Changes  of  Level.  —  It  has  been 
remarked  that  the  many  alternations  of  the  coal-beds  with 
sandstones,  shales,  conglomerates,  and  limestones  (page  245), 


CARBONIFEROUS  AGE.  265 

are  evidence  of  as  many  alternations  of  level,  or  at  least  of 
conditions,  during  the  era.  After  the  great  marshes  of  the 
Continental  Interior  had  been  long  under  verdure,  the  salt 
waters  began  again  to  encroach  upon  them  in  consequence  of 
a  sinking  of  the  land,  and  finally  swept  over  the  whole  surface, 
destroying  the  terrestrial  and  fresh-water  life  of  the  area,- — that 
is,  the  terrestrial  and  fresh-water  Plants,  Mollusks,  Insects,  and 
Reptiles,  —  but  distributing  at  the  same  time  the  new  life  of 
the  salt  waters.  Then,  after  another  long  period,  one  perhaps 
of  many  oscillations  in  the  water-level,  in  which  sedimentary 
beds  in  many  alternations  were  formed,  the  continent  again 
rose  to  aerial  life,  and  the  marshes  and  shallow  lakes  were 
luxuriant  anew  with  the  Carboniferous  vegetation.  Thus  the 
sea  prevailed  at  intervals  —  intervals  of  long  duration  — 
through  the  era  even  of  the  Coal-measures ;  for  the  associated 
sedimentary  beds,  as  has  been  stated,  are  at  least  fifty  times 
as  thick  as  the  coal-beds.  In  the  Nova  Scotia  Coal  area,  the 
waters  which  came  in  over  the  coal-beds  were  the  brackish 
or  fresh  waters  of  a  great  estuary,  —  that  at  the  mouth  of  the 
St.  Lawrence  River  of  the  Carboniferous  period. 

These  oscillations  continued  until  3,000  to  4,000  feet  of 
strata  were  formed  in  Pennsylvania,  and  over  14,000  in  Nova 
Scotia. 

The  Carboniferous  period  was,  therefore,  ever  varying  in 
its  geography.  A  map  of  its  condition  when  the  great  coal- 
beds  were  accumulating  would  have  its  eastern  coast-line  not 
far  inside  of  the  present,  and  in  the  region  of  Nova  Scotia 
and  New  England  even  outside  of  the  present ;  for  there  must 
have  been  a  sea-barrier  in  order  that  the  deposits  in  the  for- 
mer region  should  have  been  of  brackish  or  fresh- water  origin. 
The  southern  coast-line  would  pass  through  central  Carolina, 
Georgia,  Alabama,  and  Northern  Mississippi,  then  west  of 
the  Mississippi,  around  Arkansas  and  the  bordering  counties 
of  Texas ;  thence  it  would  stretch  northward,  bounding  a 
sea  covering  a  large  part  of  the  Rocky-Mountain  region,  for 
the  Coal  period  was,  in  that  part  of  the  continent,  mainly  a 


266  PALEOZOIC  TIME. 

time  of  limestone-making.  On  the  contrary,  in  a  map  repre- 
senting it  during  the  succeeding  times  of  submergence,  the 
coast-line  would  run  through  Southeastern  New  England,  then 
near  the  southern  boundary  of  New  York  State,  then  north- 
westward around  Michigan,  then  southward  again  to  Northern 
Illinois,  and  then  westward  and  northwestward  to  the  Upper 
Missouri  region,  or  the  Rocky  Mountain  sea.  Through  these 
conditions,  as  the  extremes,  the  continent  passed  several 
times  in  the  course  of  the  Carboniferous  period. 

6.  Condition  in  the  Permian  Period.  —  Finally,  in  the  Permian 
period,  the  Appalachian  region,  and  the  Interior  region  east 
of  a  north-and-south  line  running  through  Missouri,  appear 
to  have  been  mainly  above  the  ocean ;  for  the  Permian  beds 
are  mostly  confined  to  the  meridians  of  Kansas  and  the 
remoter  West. 


GENERAL  OBSERVATIONS  ON  THE  PALEOZOIC. 

1.  Rocks,  —  7.  Maximum  thickness.  —  The  maximum  thick- 
ness of  the  rocks  of  the  Silurian  age  in  North  America  is  at 
least  25,000  feet ;  of  the  Devonian,  about  14,400  feet ;  and  of 
the  Carboniferous  age,  about  16,000  feet. 

2.  Diversities  of  the  different  Continental  regions  as  to  kinds  of 
rocks.  —  The  Paleozoic  rocks  of  the  Appalachian  region  are 
mainly  sandstones,  shales,  and  conglomerates ;  only  about  one 
fourth  in  thickness  of  the  whole  consists  of  limestone.     The 
rocks  of  the  Interior  Continental  are  mostly  limestone,  full 
two  thirds  being  of  this  nature. 

The  difference  of  these  two  regions,  in  this  particular,  will 
be  appreciated  on  comparing  the  following  general  section  of 
the  strata  of  the  Interior  with  the  section,  on  page  193,  of  the 
rocks  of  New  York,  —  New  York  State  lying  on  the  inner 
border  of  the  Appalachian  region.  The  Lower  Silurian  beds 
in  the  Mississippi  basin,  as  the  section  shows,  consist  mainly 
of  limestones  ;  so  also  the  Upper  Silurian,  Devonian,  and  Sub- 
carboniferous  formations ;  and  the  Carboniferous  of  the  region 


GENERAL   OBSERVATIONS. 


267 


contains  more  limestone  than  that  of  the  East.  In  the  Devo- 
nian of  the  Interior  the  Hamilton  is  represented  by  a  lime- 
stone in  parts  of  Michigan,  Ohio,  Canada  West,  and  Illinois, 
to  Iowa,  and  besides  this  there  is  only  a  black  shale,  one  to 
three  or  four  hundred  feet  thick. 

In  the  Eastern-border  region,  about  the  Gulf  of  St.  Law- 
rence, there  is  a  great   predominance  of  limestones  in  the 


Permian 


Carboniferous 


Subcarboniferous  -| 


('In- in ii MI:  .... 
Hamilton 

Corniferous. 

Niagara  

Cincinnati 

Trenton 

Canadian 
'Potsdam 


Coal  Conglomerate. 
Subcarboniferous  limestone. 

Subcarboniferous  sandstone. 
Black  shale. 
Cliff  limestone. 

Blue  limestone  and  shale. 

Trenton  limestone  ;  Galena 
limestone ;  Black  River 
limestone. 

Lower  Magnesian  limestone 
(=  Calciferous). 

Potsdam  sandstone. 


of  the  Paleozoic  rocks  in  the  Mississippi  basin. 


formations.  They  prove  the  existence  in  that  region  of  an 
Atlantic-border  basin  similar  in  some  respects  to  the  basin  of 
the  Interior,  —  the  two  being  separated  by  the  Green  Moun- 
tains, that  is,  the  northern  part  of  the  Appalachian  region. 

3.  Diversities  of  the  Appalachian  and  Interior- Continental  regions 
as  to  the  thickness  of  the  rocks.  —  In  the  Appalachian  region 
the  maximum  thickness  of  the  Paleozoic  rocks  is  about  40,000 
feet.  But  this  thickness  is  not  observed  at  any  one  locality, 
it  being  obtained  by  adding  together  the  greatest  thicknesses 
of  the  several  formations  wherever  observed.  The  greatest 
actual  thickness  in  Pennsylvania  is  about  30,000  feet,  01 
nearly  six  miles. 


268  PALEOZOIC   TIME. 

In  the  central  portions  of  the  Interior-Continental  region 
the  thickness  varies  from  3,500  feet  (and  still  less  on  the 
northern  border)  to  6,000  feet ;  and  it  is,  therefore,  from  one 
lixtli  to  one  tenth  that  in  the  Appalachian  region. 

4.  Origin  of  the  deposits.  —  The  material  of  the  fraymental 
rocks,  or  those  of  sand,  clay,  mud,  pebbles  (the  sandstones, 
shales,  earthy  sandstones  and  conglomerates),  was  made  (1) 
by  the  wear  of  pre-existing  rocks  under  the  action  of  water ; 

(2)  by  disintegration  produced  by  partial  decomposition ;  and 

(3)  by  disaggregation  from  expansion  and  contraction  due  to 
daily  and  annual  changes  of  temperature.     The  water  was 
mainly  that  of  the  ocean,  and  the  power  was  that  of  its  waves 
and  currents.     But  the  water  from  the  rains  aided  in  the 
wear,  although  there  were  no  large  rivers ;  and,  through  the 
carbonic  acid  it  took  up  from  the  atmosphere,  it  was  a  great 
agent  in  the  disintegration  of  exposed  rocks,  —  feldspar,  the 
most  common  ingredient  in  crystalline  rocks  and  also  nearly 
all  iron-bearing  minerals,  yielding  more  or  less  easily  under 
the  action. 

The  material  of  the  coarser  rocks  may  have  accumulated 
where  the  waves  were  dashing  against  a  beach  or  an  exposed 
sand-reef,  or  else  where  currents  were  in  rapid  movement 
over  the  bottom;  for  accumulations  of  pebbles  and  coarse 
sand  are  now  made  under  these  circumstances.  The  material 
of  the  earthy  sandstones  may  have  been  the  mud  or  earthy 
sands  forming  the  bottom  of  shallow  seas.  The  fine  clayey 
or  earthy  deposits  must  have  been  made  in  either  sheltered 
bays  or  interior  seas,  in  which  the  waves  were  light,  and 
therefore  fitted  to  produce  by  their  gentle  attrition  the  finest 
of  mud ;  or  else  in  the  deeper  off-shore  waters,  where  the  finer 
detritus  of  the  shores  is  liable  to  be  borne  by  the  currents. 

Accumulations  of  any  degree  of  thickness  may  be  made  in 
shallow  waters,  provided  the  region  is  undergoing  very  slow 
subsidence ;  for  in  this  way  the  depth  of  the  waters  may  be 
kept  sufficient  to  allow  of  constantly  increasing  depositions. 
Thus,  by  a  slow  subsidence  of  1,000  feet,  deposits  1,000  feet 


GENERAL  OBSERVATIONS.  269 

thick  may  be  produced,  and  the  depth  of  water  at  no  time 
exceed  20  feet.  The  occurrence  of  ripple-marks,  mud-cracks, 
or  rain-drop  impressions  in  many  beds  of  most  of  the  forma- 
tions proves  that  the  layers  so  marked  were  successively  near 
the  surface,  and  therefore  that  there  must  have  been  a  grad- 
ual sinking  of  the  bottom  as  the  beds  were  formed. 

The  limestones  of  the  Paleozoic  were  probably  made,  in 
every  case,  out  of  organic  remains,  either  Shells,  Corals,  Cri- 
noids,  etc.,  or  the  minute  Khizopods,  which  are  known  to 
have  formed,  to  a  large  extent,  the  chalk-beds  of  Europe. 
Shells,  Corals,  and  Crinoids  must  be  ground  up  by  the  waves  to 
form  fine-grained  rocks ;  while  the  shells  of  Ehizopods  are  so 
minute  as  to  be  already  fine  grains,  and  may  become  compact 
rocks  by  simple  consolidation. 

The  hornstone  in  the  limestones,  as  remarked  on  page  234, 
may  be  wholly  of  organic  origin. 

2.  Time-Ratios.  —  Judging  from  the  maximum  thickness  of 
the  rocks  of  the  several  Paleozoic  ages  in  North  America,  and 
allowing  that  five  feet  of  fragmental  rocks  may  accumulate 
in  the  time  required  for  one  foot  of  limestone,  the  relative 
lengths  of  the  Silurian,  Devonian,  and  Carboniferous  ages 
were  not  far  from  4 :  1 :  1,  and  the  Lower  Silurian  era  was 
four  times  as  long  as  the  Upper. 

Time  moved  on  slowly  in  the  earth's  first  beginnings.  The 
condition  of  the  earth  in  an  age  of  Invertebrates,  when  all  life 
was  the  life  of  the  waters,  and  nothing  existed  above  the 
ocean's  level  except  it  may  be  the  humble  lichen  or  fungus, 
was  very  inferior  to  that  of  the  Carboniferous,  when  the  con- 
tinents had  their  forests,  the  waters  their  fishes,  and  the 
marshes  their  reptiles.  Yet  the  length  of  time  through  which 
the  earth  was  groping  under  the  first-mentioned  condition 
was  vastly  longer  than  under  the  last.  Such  is  time  in  the 
view  of  the  infinite  Creator. 

3.  Geography.  —  7.  Close  of  Archaean  time.  —  The  map  on  page 
199  shows  approximately  the  outline  of  the  dry  land  of  North 
America  at  the  close  of  the  Archsean.     The  only  mountains 


270  PALEOZOIC   TIME. 

were  Archaean  mountains,  the  principal  of  which  were  the 
Laurentiau  of  Canada,  the  Adirondacks  of  Northern  New  York, 
the  Highlands  of  New  Jersey  and  Dutchess  County  of  New 
York,  the  Blue  Eidge  farther  to  the  southwest,  and  the  Wind- 
River  and  other  eastern  ridges  of  the  Rocky  Mountain  region. 
We  cannot  judge  of  the  height  of  these  mountains  then  from 
what  we  now  see,  after  all  the  ages  of  Geology  have  passed 
over  them,  for  the  elements  and  running  water  have  never 
ceased  action  since  the  time  of  their  uplift,  and  the  amount 
of  loss  by  degradation  must  have  been  very  great. 

2.  General  Progress  through  Paleozoic  time.  —  The  increase  of 
dry  land  during  the  Paleozoic  has  been  shown  (pages  225, 239) 
to  have  taken  place  mainly  along  the  borders  of  the  Archaean, 
so  that  the  original  area  was  thus  gradually  extending.     This 
increase  is  well  marked  from  north  to  south  across  New  York. 
At  the  close  of  the  Lowe*  Silurian  the  shore-line  was  not  far 
from  the  present  position  of  the  Mohawk,  indicating  but  a 
slight  extension  of  the  dry  land  in  the  course  of  this  very 
long  era;  when   the   Upper   Silurian   ended,  the   shore-line 
probably  extended  along  a  score  of  miles  or  so  south  of  the 
Mohawk.     When  the  Devonian  ended  and  the  Carboniferous 
age  was  about  opening,  the  coast-line  was  just  north  of  the 
Pennsylvania  boundary. 

The  progress  southward  was  at  an  equal  rate  in  Wisconsin, 
where  there  is  an  isolated  Archsean  region  like  that  of  North- 
ern New  York.  In  the  intermediate  district  of  Michigan  the 
coast  made  a  deep  northern  bend  through  the  Silurian  and 
Devonian.  In  the  Carboniferous  the  same  great  Michigan 
bay  existed  during  the  intervals  of  submergence ;  but  it  was 
changed  to  a  Michigan  marsh  or  fresh-water  lake,  filled  with 
Coal-measure  vegetation,  during  the  intervening  portions  of 
the  Carboniferous  period  ;  and,  at  the  same  times,  as  explained 
on  page  265,  the  continent  east  of  the  western  meridian  of 
Missouri  had  nearly  its  present  extent,  though  not  its  moun- 
tains or  its  rivers. 

3.  Regions  of  rock-making,  and  their  differences.  —  The  sub- 


GENERAL  OBSERVATIONS.  271 

merged  part  of  the  continent  included  far  the  larger  portion, 
and  was  the  scene  of  nearly  all  the  rock-making.  Areas  of 
fresh-water,  however,  existed  at  times,  especially  in  the  Devo- 
nian and  Carboniferous,  as  is  proved  by  the  coal  beds,  and  by 
occasional  fresh-water  shells  in  shales  and  sandstones. 

The  rocks,  as  partially  explained  on  page  269,  varied  in  kind 
with  the  depth,  and  with  the  exposure  to  the  open  sea. 

This  Interior  Continental  region,  which  was  for  the  most  of 
the  time  a  great  interior  oceanic  sea,  afforded  the  conditions 
fitted  for  the  growth  of  Corals  and  Crinoids  and  other  clear- 
water  species,  and  hence  for  the  making  of  limestone  reefs 
out  of  their  remains  ;  for  limestones  are  the  principal  rocks 
of  the  interior.  Yet  there  were  oscillations  in  the  level ;  for 
there  are  abrupt  transitions  in  the  limestones,  and  some  sand- 
stones and  shales  alternate  with  them.  But  these  oscillations 
were  not  great,  the  whole  thickness  of  the  rocks,  as  stated  on 
page  268,  being  small. 

The  Appalachian  region,  on  the  contrary,  presented  the 
conditions  required  for  fragmental  deposits.  It  was  appar- 
ently a  region  of  immense  sand-reefs  and  mud-flats,  with 
bays,  estuaries,  and  extensive  submerged  off-shore  plateaus. 
Here  the  change  of  level  was  very  great;  for  within  this 
region  occur  nearly  six  miles  of  Paleozoic  formations  (page 
267).  This  vast  thickness  indicates  that  while  there  were 
various  upward  and  downward  movements  over  this  Appala- 
chian region  through  Paleozoic  time,  the  downward  move- 
ments exceeded  the  upward  even  by  the  amount  just  stated. 
These  movements  were  in  progress  from  the  Potsdam  period 
onward;  the  formations  of  nearly  every  period  exceed  8  to 
10  times  the  thickness  they  have  over  the  Interior  region. 

4.  Mountains  of  Paleozoic  origin.  —  The  mountains  in  Eastern 
North  America,  made  in  the  course  of  the  Paleozoic  ages, 
were  few.  Those  of  the  region  south  of  Lake  Superior  about 
Keweenaw  Point,  and  to  the  west,  probably  rose  during  the 
Canadian  period,  the  second  of  the  Lower  Silurian.  The 
Green  Mountain  region  became  dry  land  after  the  close  of  the 


272  PALEOZOIC  TIME. 

Lower  Silurian  (page  2 16);  but  there  is  no  reason  to  believe 
that  it  was  at  its  present  level,  for  the  Hudson  Eiver  Valley 
east  of  Hudson,  and  part  or  all  of  the  Connecticut  Valley,  was 
beneath  the  ocean,  and  became  covered  by  crinoidal  and  coral 
reefs  and  other  formations  during  the  Lower  Helderberg  era, 
and  perhaps  also  during  the  early  Devonian.  The  Devonian 
and  other  beds  of  the  vicinity  of  Gaspe,  and  of  Nova  Scotia 
and  New  Brunswick,  were  raised  into  ridges  before  the  Car- 
boniferous age  began,  mountain-making  having  gone  forward 
in  this  Atlantic-border  region  after  the  close  of  the  Devonian. 
But  the  larger  part  of  the  continental  area  remained  without 
mountains.  The  Eocky  chain  had  only  some  ridges  as  isl- 
ands in  the  seas,  and  the  Appalachians  south  of  New  England 
were  yet  to  be  made. 

5.  Rivers ;  Lakes.  —  The  depression  between  the  New  York 
and  the  Canada  Archaean,  dating  from  Archaean  time,  was 
the  first  indication  of  a  future  St.  Lawrence  channel.  It  con- 
tinued to  be  an  arm  of  the  sea,  or  deep  bay,  through  the  Si- 
lurian, and  underwent  a  great  amount  of  subsidence  as  it 
received  its  thick  formations.  After  the  Silurian  age  marine 
strata  ceased  to  form,  indicating  thereby  that  the  sea  had  re- 
tired ;  and  fresh  waters,  derived  from  the  Archaean  heights  of 
Canada  and  New  York,  probably  began  their  flow  along  its 
upper  portion,  and  emptied  into  the  St.  Lawrence  Gulf  of  the 
time  not  far  below  Montreal. 

The  raising  of  New  York  State  out  of  water  at  the  close 
of  the  Devonian  suggests  that  from  that  time  the  Hudson 
Valley  was  a  stream  of  fresh  water.  The  valley  itself,  and 
its  continuation  north  as  the  Champlain  Valley,  date 
from  the  close  of  the  Lower  Silurian,  if  not  from  the  Ar- 
chaean. 

The  Mississippi  and  its  tributaries,  east  and  west,  were  not 
in  existence  in  the  Paleozoic  ages.  In  the  intervals  of  Car- 
boniferous verdure,  when  the  continent  was  emerged,  the 
Ohio  and  Mississippi  basin  were  regions  of  great  marshes, 
lakes,  and  bayous,  and  not  of  great  rivers ;  for  rivers  could 


GENERAL  OBSERVATIONS.  273 

not  exist  without  a  head  of  high  land  to  supply  water  and 
give  it  a  flow. 

Over  portions  of  Lake  Superior  there  were  extensive  rock- 
deposits  and  igneous  eruptions  in  part  of  the  Canadian  period ; 
and  the  thick  accumulations  show  that  deep  subsidences  were 
then  in  progress  there,  as  also  in  the  region  of  the  St.  Law- 
rence ;  so  that  we  may  infer  that  the  basin  of  this  great  lake 
was  already  in  process  of  formation  before  the  Lower  Silurian 
closed.  The  extent  and  position  of  the  great  Michigan  bay 
through  the  Silurian  and  Devonian  ages  and  much  of  the 
Carboniferous,  as  mentioned  on  pages  225,  264,  show  that 
Lakes  Erie,  Huron,  and  Michigan  were  then  within  the  lim- 
its of  this  bay.  Whether  deeper  or  not  than  other  portions 
of  the  bay,  is  not  known. 

Thus,  Geology  studies  the  Geography  of  the  Paleozoic  ages, 
and  traces  North  America  through  its  successive  stages  of 
growth. 

4.  Climate.  —  No  evidence   has   been   found  through   the 
Paleozoic  records  of  any  marked  difference  of  temperature 
between  the  zones.     In  the  Carboniferous  age  the  Arctic  seas 
had  their  Corals  and  Brachiopods,  and  the  Arctic  lands  their 
forests  and  marshes  under  dense  foliage,  no  less  than  those  of 
America  and  Europe.     The  facts  on  this  subject  are  stated  on 
page  262. 

5.  Life.  —  7.  Appearance  and  disappearance  of  species.  —  With 
the  beginning  and  progress  of  each  formation  in  the  series, 
new  species  appeared,  and  the  old  ones  more  or  less  com- 
pletely disappeared.     Such  changes  in  the  life  occurred  in 
connection  even  with  the  minor  transitions  in  the  rock-for- 
mations, as  in  that  from  a  bed  of  shale  to  sandstone  or  to 
limestone,  and  the  reverse.     Thus,  through  the  ages,  life  and 
death  were  in  concurrent  progress. 

2.  Beginning  and  ending  of  genera,  families,  and  higher  groups. 
-  The  following  table  of  the  tribe  of  Trilobites  illustrates  the 
progress  which  took  place  in  this  group  and  exemplifies  the 
general  fact  with  regard  to  other  tribes  :  — 

18 


274 


PALEOZOIC   TIME. 


Trilobites 

Paradoxides 

Bathy  urus 

Asaphus,  Remopleurides 


Calymene,  Ampyx,   Illaenus,   Acidaspis, 
and  Ceraurus 

Homalonotus  and  Lichas 

Phillipsia,  Griffithides 


Silurian. 


Dev.    Garb. 


Lower. 


Upper 


P.  Pd 


C.  P 


The  vertical  columns  correspond  to  the  Lower  and  Upper 
Silurian,  the  Devonian,  and  the  Carboniferous.  The  left- 
hand  column  under  Lower  Silurian  corresponds  to  the  first, 
or  Primordial  period ;  and  the  three  columns  under  the  Car- 
boniferous, to  the  Subcarboniferous,  Carboniferous,  and  Per- 
mian periods  of  the  age.  Opposite  TRILOBITES,  the  black  area 
shows  that  the  tribe  began  with  the  beginning  of  the  Paleo- 
zoic and  continued  nearly  to  its  end.  Next  there  is  the  name 
of  a  genus  which  existed  only  in  the  Primordial  period,  it 
having  then  many  species,  but  none  afterward ;  with  it  there 
were  other  genera  which  had  species  also  in  the  later  part  of 
the  Lower  Silurian.  Then  there  is  a  genus,  Bathyurus,  which 
continued  from  the  Primordial  through  the  Lower  Silurian. 
Then,  others  confined  to  the  rest  of  the  Lower  Silurian ;  others 
that  passed  into  the  Upper  Silurian,  then  to  become  extinct ; 
others  that  continued  into  the  Devonian;  and  two  genera 
confined  to  the  Carboniferous. 

In  a  similar  manner  the  genera  and  families  of  Brachiopods 
began  at  different  periods  or  epochs,  and  continued  on  for  a 
while,  to  become,  in  general,  extinct.  Many  genera  ended  in 
the  course  of  the  Paleozoic  and  at  its  close ;  only  a  few  con- 
tinued into  later  periods. 


GENERAL   OBSERVATIONS.  275 

3.  Special  Paleozoic  psculiarities  of  the  Life.  — The  following 
facts  show  in  what  respects  the  life  of  the  Paleozoic  ages  was 
peculiarly  ancient :  — 

a.  Not  only  are  the  species  all  extinct,  but  almost  every 
genus.     Fifteen  or  sixteen  of  the  genera  which  existed  in  the 
course  of  the  Paleozoic  have  living  species ;  and  all  these  are 
Molluscan. 

b.  Among  Eadidtes,  the  Polyps  were  largely  of  the  tribe  of 
Cyatlwplvylloid  corals,  which  is  almost  exclusively  ancient  or 
Paleozoic.     The  Echinoderms  were  mostly  Crinoids,  and  these 
were  in  great  profusion.     Crinoids  were   far  less  abundant, 
and  of  different  genera,  in  the  Mesozoic ;  and  now,  few  exist. 

c.  Among  Mollusks,  Bracliiopods  were  exceedingly  abun- 
dant :  their  fossil  shells  far  outweigh  those  of  all  other  Mol- 
lusks.    But  in  the  Mesozoic  they  were  much  less  numerous 
than   other   Mollusks ;    and  at   the   present  time  the  group 
is  nearly  extinct.     The  Cephalopoda  were  represented  very 
largely  by  Orthoceratx,  but  few  species  of  which  existed  in 
the  early  Mesozoic,  and  none  afterward. 

d.  Among  Articulates,  Trilobites  were  the  most  common 
Crustaceans,  —  a  group  exclusively  Paleozoic. 

e.  Among  Vertebrates,  the  Devonian  Fishes  were  either 
Ganoids,  Placoderms,  or  Selachians,  and  the  Ganoids  had  verte- 
brated  tails.     Of  this  kind  of  Ganoids,  but  few  species  lived 
in  the  first  period  of  the  Mesozoic ;  and  the  whole  group  of 
Ganoids  is  now  nearly  extinct.     Of  the  Selachians,  a  large 
proportion  were  Cestracionts,  —  a  tribe  common  in  the  Meso- 
zoic, but  now  nearly  extinct. 

/.  Among  terrestrial  Plants,  there  were  Lepidodendrids, 
Siyillarids,  Catamites  in  great  profusion,  making,  with  Conifers 
and  Ferns,  the  forests  and  jungles  of  the  Carboniferous  and 
later  Devonian  :  no  Lepidodendrid  or  Sigillarid  existed  after- 
ward, and  the  Catamites  ended  in  the  Mesozoic. 

Thus,  the  Paleozoic  or  ancient  aspect  of  the  animal  life  was 
produced  through  the  great  predominance  of  Brachiopods,  Cri- 
noids, CyathophyllM  Corals,  Orthocerata,  Trilobites,  and  verte- 


276  PALEOZOIC  TIME. 

brated-tailed  Ganoids ;  and  that  of  the  plants  over  the  land, 
through  the  Lepidodendrids,  Sigillarids,  and  Calamites,  along 
with  the  Ferns  and  Conifers.  In  addition  to  this  should  be 
mentioned  the  absence  of  Angiosperms  and  Palms  among 
Plants ;  the  absence  of  Teliost  Fishes,  and  of  Birds  and  Mam- 
mals, among  Vertebrates ;  and  of  nearly  all  modern  tribes  of 
genera  among  Radiates,  Mollusks,  and  Articulates. 

4.  Mesozoic  and  Modern  types  begun  in  Paleozoic  time.  —  The 
principal  Mesozoic  type  which  began  in  the  Paleozoic  was  the 
Reptilian.  But  besides  these  Reptiles  there  were  the  first  of 
the  Decapod  Crustaceans ;  the  first  of  Oysters ;  the  first  of  the 
great  tribe  of  Ammonites,  the  Goniatitcs  being  of  this  tribe ; 
the  first  of  Insects,  Spiders  and  Centipedes.  The  type  of  In- 
sects, or  terrestrial  Articulates,  belongs  eminently  to  modern 
time ;  for  it  probably  has  now  its  fullest  display. 

Thus,  while  the  Paleozoic  ages  were  progressing,  and  the 
types  peculiar  to  them  were  passing  through  their  time  of 
greatest  expansion  in  numbers  and  perfection  of  structure, 
there  were  other  types  introduced  which  were  to  have  their 
culmination  in  a  future  ase. 


DISTURBANCES   CLOSING  PALEOZOIC  TIME. 

1.  General  quiet  of  the  Paleozoic  Ages.  —  The  long  ages  ef 
the  Paleozoic  passed  with  but  few  and  comparatively  small 
disturbances  of  the  strata  of  Eastern  North  America.  There 
were  some  early  permanent  uplifts  in  the  Lake  Superior 
region,  during  the  •  Lower  Silurian ;  again,  after  the  Lower 
Silurian,  the  Green  Mountains  were  made ;  and  again,  after 
the  close  of  the  Devonian,  there  were  disturbances  and  upturn- 
ings  in  Eastern  New  Brunswick,  part  of  Nova  Scotia,  and  East- 
ern Canada  by  Gaspe  near  St.  Lawrence  Bay.  Besides  these 
changes  there  was,  through  the  ages,  a  gradual  increase  on 
the  north  in  the  amount  of  dry  land ;  and  through  parts  of 
all  the  periods,  over  a  large  part  of  the  continent,  slow  oscil- 
lations were  in  progress,  varying  the  water-level  and  favoring 


APPALACHIAN   REVOLUTION.  277 

the  increasing  thickness  of  the  rocks,  and  their  successive 
variations  as  to  kind  and  extent.  But  these  movements  of 
the  earth's  crust  were  exceedingly  slow,  —  probably  less  than 
a  foot  a  century.  There  may  have  been  many  occasional 
quakings  of  the  earth,  —  even  exceeding  the  heaviest  of 
modern  earthquakes.  There  may  have  been  at  times  sudden 
risings  or  sinkings  of  portions  of  the  continental  crust.  But 
the  condition  of  the  strata  of  the  interior  of  the  continent, 
and  of  the  Appalachian  region  south  of  the  Green  Mountains, 
indicates  that  general  quiet  prevailed  through  the  long  Paleo- 
zoic ages. 

2.  The  Appalachian  the  region  of  greatest  change  of  level 
through  the  Paleozoic,  —  The  region  of  greatest  movement  dur- 
ing these  ages  was  the  Appalachian.     For  it  has  been  showTn 
that  the  oscillations  which  there  took  place  resulted  in  sub- 
sidences of  one  or  more  thousand  feet  with  nearly  every  period 
of  the  Paleozoic.     In  the  Green  Mountain  portion  the  oscilla- 
tions ceased  after  the  close  of  the  Lower  Silurian  era ;  but  not 
until  the  subsidence  there  had  reached  probably  15,000  feet; 
and  in  Pennsylvania  and  Virginia  they  continued  through  a 
large  part  of  the  Carboniferous  age,  until  the  sinking  amounted 
to  about  30,000  feet.     But  this  sinking  was  quiet  in  its  prog- 
ress, as  is  proved  by  the  regularity  in  the  series  of  strata. 

The  thickness  of  the  coal-beds  indicates  that  the  coal-plant 
marshes  were  long  undisturbed,  and  therefore  that  long  periods 
passed  without  appreciable  movement. 

3.  Approach  of  the  epoch  of  Appalachian  revolution.  —  The 
era  of  comparative  quiet  alluded  to  came  gradually  to  a  close 
as  the  Carboniferous  age  was  terminating,  and  an  epoch  of 
upturning  and  mountain-making  began.     There  are  mountains 
to  testify  to  this  both  in  Europe  and  America. 

In  Eastern  North  America  the  disturbances  affected  Nova 
Scotia  and  the  coal  area  of  Ehode  Island  and  Southeastern 
Massachusetts ;  and,  with  far  grander  results,  the  Appalachian 
region  and  Atlantic  border  from  Southern  New  York  to  Ala- 
bama. The  Appalachian  mountains  are  a  part  of  the  result, 


278  CLOSE  OF  PALEOZOIC  TIME. 

and  hence  the  epoch  is  appropriately  styled  the  epoch  of  the 
Appalachian  revolution.  The  region  in  Eastern  America  of 
the  deepest  Paleozoic  subsidence  and  of  the  thickest  accumu- 
lation of  Paleozoic  rocks,  that  is,  the  Appalachian,  was  now  the 
region  of  the  profoundest  disturbances  and  the  greatest  uplifts. 
4.  Effects  of  the  disturbances.  —  The  fallowing  are  among 
the  effects  of  the  disturbances  along  the  Appalachian  region 
and  Atlantic  border :  — 

1.  Strata  were  upraised  and  flexed  into  great  folds,  some 
of  the  folds  a  score  or  more  of  miles  in  span. 

2.  Deep    fissures   of   the  earth's   crust  were   opened,  and 
faults  innumerable  were  produced,  some  of  them  of  10,000 
to  20,000  feet. 

3.  Eocks  were   consolidated;   and  over   some  parts  sand- 
stones and  shales  were  crystallized  into  gneiss,  mica  schist, 
and  other  related  rocks,  and  limestone  into  architectural  and 
statuary  marble. 

4.  Bituminous  coal  was  turned  into  anthracite  in   Penn- 
sylvania and  Rhode  Island. 

5.  In  the  end,  the  Appalachian  mountains  were  made. 

5.  Evidence   of  the  flexures,  uplifts,   and  metamorphism.  — 
The  evidence  that  the  rocks  of  the  Appalachian  region  and 
Atlantic  border  were  flexed,  uplifted,  faulted,  and  otherwise 
changed  from  their  original  condition,  is  as  follows  :  — 

The  Coal-measures  and  other  Paleozoic  strata,  though 
originally  spread  out  in  horizontal  beds,  are  now  in  an  uplifted 
and  flexed  or  folded  condition  ;  and  they  are  so  involved  to- 

Fig.  312. 


Section  at  Trevorton  Gap,  Pa.,  the  dark  bands  representing  coal  beds. 

gether  in  one  system  of  flexures  and  uplifts  that  the  whole 
must  have  been  the  result  of  one  system  of  movements. 
Figs.  312-315  illustrate  this, 


APPALACHIAN   REVOLUTION. 


279 


Figs.  312  and  313,  and  120  on  page  160,  represent  sec 
tions  in  the  coal  regions  of  Pennsylvania.     In  Fig.  313,  the 


Fig.  313. 


Section  on  the  Scliuylkill,  Pennsylvania  ;  P.,  Pottsville  on  the  Coal-measures  ;  2,  Calciferous 
formation  ;  3,  Trenton  ;  4,  Hudson  River  ;  5,  Oueida  and  Niagara  ;  7,  Lower  Helcierberg  ; 
8,  10,  11,  Devonian  ;  12,  13,  Subcarbonherous  ;  14,  Carboniferous  or  Coal-measures. 

coal-beds  are  the  upper  to  the  left,  numbered  147  the  rest  are 
beds  of  underlying  Paleozoic  formations,  as  explained  under 
the  figure.  Fig.  120  shows  the  complicated  folds  in  the  an- 
thracite coal  measures,  near  Mauch  Chunk;  three  steep  anti- 
clines occur  in  1,200  yards. 

Fig.  314. 


I  S.E. 


Section  from  the  Great  North  to  the  Little  North  Mountain  through  Bore  Springs,  Virginia  ; 
t,  t,  position  of  thermal  springs  ;  n,  Calciferous  formation  ;  in,  Trenton  ;  iv,  Hudson 
River  ;  v,  Oneida  ;  vi,  Clinton  and  Lower  Helderberg  ;  vn,  Oriskauy  Sandstone  and 
Cauda-Galli  Grit. 

Fig.  314  was  taken  from  the  vicinity  of  Bore  Springs,  in 
Virginia,  and  includes  Silurian  and  Devonian  beds. 


L-vjtion  of  the  Paleozoic  formations  of  the  Appalachians  in  Southern  Virginia,  between 
Walker's  Mt.  and  the  Peak  Hills  (near  Peak  Creek  Valley) :  F,  fault ;  a,  Lower  Silurian 
limestone  ;  b,  Upper  Silurian  ;  c,  Devonian  ;  d,  Subcarboniferous,  with  coal-beds. 

Fig.    315   represents   one  of    the   great   faults    in    South- 
ern Virginia  (between  Walkei  's  Mountain  and  Peak  Hills) ; 


280  CLOSE   OF  PALEOZOIC   TIME. 

the  break  is  at  F,  and  the  rocks  on  the  left  were  shoved 
up  along  the  sloping  fracture  until  a  Lower  Silurian  lime- 
stone (a)  was  on  a  level  with  the  Subcarboniferous  formation 
(d),  a  fault  of  more  than  10,000  feet.  Such  examples  are 
in  great  numbers  throughout  the  Appalachians.  In  many 
of  the  transverse  valleys  the  curves  may  »be  traced  for  scores 
of  miles. 

As  shown  in  the  above  sections  (Figs.  312-315),  the  folds, 
instead  of  remaining  in  regular  rounded  ridges  with  even 
synclinal  valleys  between,  such  as  the  flexing  of  the  strata 
might  make,  have  been  to  a  great  extent  worn  away,  or  mod- 
elled into  new  ridges  and  valleys,  by  the  action  of  waters 
during  subsequent  time ;  and  often  what  was  the  top  of  a  fold 
is  now  the  bottom  of  a  valley,  because  the  folds  would  be 
moot  broken  where  most  abruptly  bent,  —  that  is,  along  the 
axes  of  upward  flexure,  —  and  hence  would  be  most  liable  in 
these  parts  to  be  cut  away  or  gorged  out  by  any  denuding 
causes.  The  figures  on  page  57  illustrate  still  further  the 
condition  of  folded  strata  before  and  after  denudation.  Some 
of  the  Appalachian  folds  were  probably  20,000  feet  in  height 
above  the  present  level  of  the  ocean,  or  would  have  had  this 
height  if  they  had  remained  unbroken,  while  in  fact  the 
loftiest  summits  now  are  less  than  5,000  feet,  and  few  exceed 
3,000  feet. 

Over  New  England  there  are  similar  flexures.  Those  of 
the  Rhode  Island  coal-formation  are  very  abrupt,  and  full  of 
faults,  the  coal-beds  being  much  broken  and  displaced. 

6.  General  truths  with  regard  to  the  results.  —  The  follow- 
ing are  some  of  the  general  truths  connected  with  the  uplifts 
and  metamorphism  :  — 

1.  The  courses  of  the  flexures  and  of  the  outcrops  or 
strike,  and  those  of  the  great  faults,  are  approximately  north- 
east, or  parallel  to  the  Atlantic  border.  There  is  a  bend 
eastward  in  Pennsylvania  corresponding  with  the  eastward 
bend  of  the  southern  coast  of  New  England,  and  then  a  change 
to  the  northward  in  New  England. 


APPALACHIAN   REVOLUTION.  281 

2.  The  folds  have  their  steepest  slope  toward  the  northwest, 
or  away  from  the  ocean.     If  Fig.  49  (page  57)  represent  one 
of  the  folds,  the  left  would  be  the  ocean  side,  or  that  to  the 
southeast,  and  the  right  the  landward  side,  or  that  to  the 
northwest. 

3.  The  flexures  are  most  numerous  and  most  crowded  on 
that  side  of  the  Appalachian  region  which  is  toward  the  ocean, 
and  diminish  westward.     There  is  seldom,  however,  a  gradual 
dying  out  westward,  the  region  of  disturbance  being  often 
bounded  on  the  west  by  one  or  more  of  the  great  fractures 
and  faults,  as  in  Eastern  Tennessee  and  along  the  valley  of 
the  Hudson. 

4.  The  consolidation  and  metamorphism  of  the  strata  are 
more  extensive  and  complete  to  the  eastward  (or  toward  the 
ocean)  than  to  the  westward. 

5.  The  change  of  bituminous  coal  to  anthracite,  by  the 
expulsion  of  volatile  ingredients,  was  most  complete  where 
the  disturbances  were  greatest,  —  that  is,  in  the  more  eastern 
portions  of  the  coal  areas.     The  anthracite  region  of  Penn- 
sylvania (see  map,  p.  242)  owes  its  broken  character  partly 
to  the  uplifts  and  partly  to  denudation.     To  the  westward 
the  coal  is  first  semi-bituminous,  and  then,  as  at  Pittsburg, 
true   bituminous.     In  Pthode    Island,  where   the    associated 
rocks  are  partly  true  metamorphic  or  crystalline  rocks  and  the 
disturbances  are  very  great,  the  coal  is  an  extremely  hard 
anthracite,  and  in  some  places  is  altered  to  graphite,  —  an 
effect  which  may  be  produced  in  ordinary  coal  by  the  heat 
of  a  furnace. 

7,  Conclusions.  —  These  facts  lead  to  the  following  conclu- 
sions :  — 

1.  The  movement  producing  these  vast  results  was  due  to 
lateral   pressure,  the  folding  having  taken  place  just  as  it 
might  in  paper  or  cloth  under  a  lateral  or  pushing  movement. 

2.  The  pressure  was  exerted  at  right  angles  to  the  courses 
of  the  folds,  as  is  the  case  when  paper  is  folded  in  the  manner 
mentioned. 


282  CLOSE   OF  PALEOZOIC  TIME. 

3.  The  pressure  was  exerted  from  the  ocean  side  of  the 
Appalachians ;  for  the  results  in  foldings  and  metamorphism 
are  most  marked  toward  the  ocean. 

4.  The  force  was  vast  in  amount. 

5.  The  force  was  slow  in  action  and  long  continued,  —  and 
not  abrupt  or  paroxysmal  as  when  a  wave  or  series  of  waves 
is  thrown  up  by  an  earthquake  shock  on  the  surface  of  an 
ocean.     For  the  strata  were  not  reduced  by  it  to  a  state  of 
chaos,  but  retain  their  stratification,  and  show  comparatively 
little  confusion,  even  in  the  regions  of  greatest  disturbance 
and  alteration. 

6.  The  action  of  the  force  was  attended  by  the  production 
of  heat.     For  without  some  heat  above  the  ordinary  tempera- 
ture, it  is  not  possible  to  account  for  the  consolidation  and 
crystallization  of  the  rocks. 

7.  The   history   of  the   Appalachian   Mountains   extends 
through  all   the  geological  ages  from  the  Archaean  onward. 
During  the  Silurian,  Devonian,  and  Carboniferous  ages  the 
formations  were  accumulating  to  a  great  thickness,  while  a 
slow  subsidence  was  in  progress.     When  the  Carboniferous 
age  was  closing,  and  the  subsidence  had  reached  a  depth  of 
several  miles,  there  were  other  movements,  producing  flexures 
of  the  strata,  uplifts,  faults,  consolidation,  and  metamorphism, 
and  ending  in  the  making  of  the  mountains.     And  finally, 
during  these  upliftings,  moving  waters  commenced  the  work 
of  denudation,  which  has  been  continued  to  the  present  time. 

8.  Disturbances  on  other  continents. — The  amount  of  con- 
temporaneous mountain-making  over  the  globe  at  this  epoch 
has  not  yet  been  clearly  made  out.     Enough  is  known  to  ren- 
der it  probable  that  the  Ural  Mountains,  with  their  veins  of 
gold  and  platinum,  were  made  at  the  same  time  with  the  Ap- 
palachians, and  that  uplifts  and  metamorphism  also  occurred 
in  other  parts  of  Europe,  and  in  Great  Britain.     Murchison 
states  that  the  close  of  the  Carboniferous  period  was  specially 
marked  by  disturbances  and  uplifts ;  that  it  was  then  "  that 
the  coal  strata  and  their  antecedent  formations  were  very 


MESOZOIC  TIME.  283 

generally  broken  up,  and  thrown,  by  grand  upheavals,  into 
separate  basins,  which  were  fractured  by  numberless  power- 
ful dislocations." 

The  epoch  of  the  Appalachian  revolution  was,  then,  a  grand 
epoch  for  the  world.  The  extermination  of  life  which  took 
place  at  the  time  was  one  of  the  most  extensive  in  all 
geological  history,  and  must  have  been  a  consequence  of  the 
great  physical  changes  progressing  over  the  earth's  surface. 
But  it  cannot  be  affirmed  that  the  extermination  was  univer- 
sal, although  no  fossils  of  the  Carboniferous  formation  occur  in 
later  rocks ;  for  these  strata,  as  they  are  confined  to  portions 
of  the  continental  seas,  testify  only  as  to  changes  and  de- 
structions throughout  those  sea^  and  not  respecting  the  life 
existing  elsewhere. 


III.  — MESOZOIO  TIME. 

1.  Ages.  —  Mesozoic  or  mediaeval  time,  in  Geological  his- 
tory, comprises  but  one  age,  —  the  EEPTILIAN.     In  the  course 
of  it  the  class  of  Eeptiles  passed  its  culmination ;  —  that  is, 
its  species  increased  in  numbers,  size,  and  diversity  of  forms, 
until  they  vastly  exceeded  in  each  of  these  respects  the  Eep- 
tiles of  either  earlier  or  later  time. 

2.  Area  of  progress  in  rock-making.  —  The  area  of  rock- 
making  in  North  America,  during  Mesozoic  time,  was  some- 
what different  from  what  it  was  in  Paleozoic.     Then,  nearly 
the  whole  continent,  outside  of  the  northern  Archaean  area, 
was  receiving  its  successive  formations  ;  and  the  three  great 
regions  were  the  Eastern  border,   the  Appalachian,  and  the 
Interior   Continental.     By  the   close   of  Paleozoic   time  the 
Appalachian  region  and  the  Interior  east  of  the  Mississippi, 
excepting  its  southern  portion,  had  become  part  of  the  dry 
land  of  the  continent,  as  is  shown  by  the  absence  of  marine 
strata  of  later  date.     The  great  areas  of  progress  were  conse- 


284  MESOZOIC   TIME.  —  REPTILIAN  AGE. 

quently  changed,  and  became  (1)  the  Atlantic  border,  (2) 
the  Gulf  border,  and  (3)  the  Western  Interior,  or  region  west 
of  the  Mississippi.  In  other  words,  the  continent,  from  the 
Mesozoic  onward,  until  the  close  of  the  Tertiary  period  in  the 
Cenozoic,  was  receiving  its  new  marine  formations  along  its 
borders,  and  in  extensive  areas  over  the  part  of  the  Interior 
region  embraced  by  the  Summit  region  and  slopes  of  the 
Eocky  Mountains. 

These  three  regions  are  continuous  with  one  another,  the 
Atlantic  connecting  with  the  Gulf  border  region  on  the  south, 
and  the  Gulf  border  region  passing  northwestward  into  the 
Western  Interior  or  Eocky  Mountain  region  and  Pacific 
border. 

In  Europe  no  analogous  change  can  be  distinguished  ;  for 
the  continent  was,  from  the  first,  an  archipelago,  and  it  con- 
tinued to  bear  this  geographical  character,  though  with  an 
increasing  prevalence  of  dry  land,  until  the  Cenozoic  era  had 
half  passed.  Western  England  then  stood  as  three  or  four 
islands  above  the  sea  (the  area  marked  as  covered  by  Paleo- 
zoic rocks  on  the  map,  page  244) ;  and  the  area  of  future  rock- 
making  was  mainly  confined  to  the  intervals  between  these 
islands  and  to  the  submerged  area  on  the  east  and  southeast. 
It  is  probable  that  this  area  and  a  portion  of  Northeastern 
France  were,  geologically,  part  of  a  large  German-Ocean  basin. 

REPTILIAN  AGE. 

Periods.  —  The  Eeptilian  Age  includes  three  periods  :  — 
7.  TnQSSic:  named  from  the  Latin  tria,  three,  in  allusion  to 
the  fact  that  the  rocks  of  the  period  in  Germany  consist  of 
three  separate  groups  of  strata.  This  is  a  local  subdivision, 
not  characterizing  the  rocks  in  Britain  or  in  most  other  parts 
of  Europe. 

2.  Jurassic:  named  from  the  Jura  Mountains,  situated  on 
the  eastern  border  of  France,  between  France  and  Switzerland, 
where  rocks  of  the  period  occur. 


TRIASSIC   AND   JURASSIC   PERIODS.  285 

8.  Cretaceous :  named  from  the  Latin  creta,  chalk,  the  chalk- 
beds  of  Britain  and  Europe  being  included  in  the  Cretaceous 
formation. 

1.  Triassic  and  Jurassic  Periods. 
I.  Rocks:  Kinds  and  Distribution. 

The  American  rocks  of  the  Triassic  period  have  not  yet 
been  separated  from  those  of  the  Jurassic,  except  in  the  re- 
gion west  of  the  Mississippi. 

In  the  Atlantic-border  region  these  rocks  occupy  narrow 
ranges  of  country  parallel  with  the  Appalachian  chain,  fol- 
lowing its  varying  courses.  One  of  these  ranges  occupies  the 
valley  of  the  Connecticut  between  Northern  Massachusetts 
and  New  Haven  on  Long  Island  Sound,  and  runs  parallel 
with  the  Green  Mountains:  it  has  a  length  of  about  110 
miles.  Another  —  the  longest  of  them  —  commences  at  the 
north  extremity  of  the  Palisades,  on  the  west  bank  of  the 
Hudson  Eiver,  and  stretches  southwestward  through  New 
Jersey,  Pennsylvania  (here  bending  much  to  the  westward, 
like  the  Appalachians  of  the  State,  as  shown  in  the  map  on 
page  242),  and  reaching  far  into  the  State  of  Virginia, 
Another  stretches  —  almost  in  the  line  of  the  last  —  through 
North  Carolina,  There  is  another  along  Western  Nova  Scotia, 
These,  and  some  other  smaller  areas,  are  indicated  on  the  map 
on  page  195  by  an  oblique  lining  in  which  the  lines  run  from 
the  right  above  to  the  left  below. 

The  rocks  are  mainly  sandstones  and  conglomerates,  but 
include  some  considerable  beds  of  shale,  and  in  a  few  places 
impure  limestone.  The  sandstones  are  generally  red  or 
brownish-red.  The  freestone  of  Portland,  near  Middletown 
in  Connecticut,  and  of  the  vicinity  of  Newark  in  New  Jer- 
sey, are  from  this  formation.  The  pebbles  and  sand  of  the 
beds  were  derived  mainly  from  metamorphic  rocks  alongside 
of  the  regions  in  which  they  lie ;  and  from  some  of  the 
coarser  layers  large  stones  of  granite,  gneiss,  and  mica  schist 


286  MESOZOIC   TIME.  — KEPTILIAN  AGE. 

may  be  taken.  The  strata  overlie  directly,  but  unconform- 
ably,  these  metamorphic  rocks.  Near  Kichmoud  in  Virginia 
and  in  North  Carolina  there  are  valuable  beds  of  bituminous 
coal. 

The  several  ranges  of  this  sandstone  formation  are  remark- 
able for  the  great  number  of  trap  dikes  and  trap  ridges  inter- 
secting them  (page  43).  Mount  Holyoke  in  Massachusetts, 
Edst  and  West  Rocks  near  New  Haven  in  Connecticut,  and 
the  Palisades  on  the  Hudson  are  a  few  examples  of  these 
trap  ridges.  Trap  is  an  igneous  rock,  one  that  was  ejected  in 
a  melted  state  from  a  deep-seated  source  of  fire,  through  fis- 
sures made  by  a  fracturing  of  the  earth's  crust.  The  dikes 
and  ridges  are  exceedingly  numerous,  and  have  the  same  gen- 
eral course  with  the  sandstone  ranges.  They  are  so  associated 
with  the  sandstone  formation  that  there  must  have  been 
some  connection  in  origin  between  the  water-made  and  the 
fire-made  rocks.  The  proofs  that  the  trap  came  up  through 
the  fissures  in  a  melted  state  are  abundant ;  for  the  wall-rock 
of  the  fissures  is  often  baked  so  as  to  be  very  hard,  and  is 
sometimes  filled  with  crystallizations,  as  of  epidote,  tourma- 
line, garnet,  hematite,  etc.,  evidently  due  to  the  heat. 

West  of  the  Mississippi,  in  the  Western  Interior  region 
southwest  of  Southern  Kansas,  there  is  a  sandstone  formation, 
containing  much  gypsum  (and  hence  called  the  gypsiferous 
formation),  but  barren  of  fossils,  except  an  occasional  frag- 
ment or  trunk  of  fossil  wood,  which  is  regarded  as  Triassic. 
Triassic  beds  occur  also  in  Colorado  and  New  Mexico,  Utah 
and  Nevada.  Along  with  Jurassic  strata  they  enter  into  the 
constitution  of  the  Elk  and  Wahsatch  mountains,  and  the 
Sierra  Nevada.  These  western  Jurassic  beds  in  many  places 
contain  fossils,  but  only  rarely  so  the  Triassic. 

In  the  vicinity  of  the  Black  Hills,  in  the  region  of  the 
Upper  Missouri,  there  are  some  beds  of  impure  limestone  con- 
taining marine  fossils  which  are  true  Jurassic. 

In  Europe,  the  Triassic  rocks  of  Eastern  France  and  Ger- 
many, east  and  west  of  the  Ehine,  consist  of  a  shell  limestone 


TRIASSIC   AND   JURASSIC   PERIODS.  287 

(called  in  German  MuscJielkalJc)  between  an  underlying  thick 
reddish  sandstone  (Buntcr  Sandsteiri)  and  overlying  strata  of 
reddish  and  mottled  marlytes  and  sandstone  (Keuper  of  the 
Germans).  In  England  (see  No.  6  on  map,  page  244),  the 
formation  consists  of  reddish  sandstone  and  marlytes ;  it  is 
mostly  confined  to  a  region  running  north-northwest  just  east 
of  the  Paleozoic  areas,  and  to  an  extension  of  this  region 
westward  to  Liverpool  bay  (or  over  the  interval  between  the 
two  main  areas)  and  up  the  west  coast. 

This  formation,  in  Europe,  contains  in  many  places  beds 
of  salt,  and  is  hence  often  called  the  Saliferous  group.  At 
Northwich  in  Cheshire,  in  England,  there  are  two  beds  of 
rock-salt,  90  to  100  feet  thick;  and  in  Europe  there  are  simi- 
lar beds  at  Vic  and  Dieuze  in  France,  and  at  Wurtemberg  in 
Germany. 

The  Jurassic  rocks  of  Britain  and  Europe  are  divided  into 
three  principal  groups  :  — 

1.  The  Liassic  (No.  7 a  on  map  of  England,  page  244),  con- 
sisting of  grayish  compact  limestone  strata,  called  Lias. 

2.  The  Odlytic  (No.  7b  on  map,  page  244),  consisting  mostly 
of  whitish  and  grayish  limestones,  part  of  them  oolitic  (page 
37).     One  stratum,  near  the  middle  of  the  series,  is  a  coral- 
reef  limestone,  much  like  the  reef-rock  of  existing  coral  seas, 
though  different  in  species  of  coral.     Near  the  top  of  the  series 
there  are  some  local  beds  of  fresh-water  or  terrestrial  origin, 
in  what  is  called  the  Purbeck  group,  and  one  on  the  island 
of  Portland  is  named,  significantly,  the  Portland  dirt-led.    The 
Solenhofen  lithographic  limestone  is  a  very  fine-grained  rock 
(thereby  fit  for  lithography),  of  the  age  of  the  Middle  Oolyte 
occurring  in  Pappenheim  in  Bavaria. 

3.  The  Wealdcn  (No.  8  on  the  map  of  England),  a  series 
of  beds  of  estuary  and  fresh-water  origin,  mostly  clay  aud 
sand,  but  partly  of  limestone.     They  occur  in  Southeastern 
England.     They  are  named   Wcalden  from  the  region  where 
first  studied,  called  the  Weald,  covering  parts  of  Kent,  Surrey, 
and  Sussex. 


288 


MESOZOIC   TIME.  — REPTILIAN  AGE. 


2.    Life. 

1.    Plants. 

The  vegetation  of  the  Triassic  and  Jurassic  periods  included 
numerous  kinds  of  Ferns,  both  large  and  small,  Catamites,  and 
Conifers,  and  so  far  resembled  that  of  the  Carboniferous  age. 
But  there  were  no  forests  or  jungles  of  Lepidodendrids  and 
Slgillarids.  Instead  of  these  Carboniferous  types,  a  group  of 
trees  and  shrubs  sparingly  represented  in  the  later  Carbon- 
iferous, that  of  the  Cycads,  was  eminently  characteristic  of 
the  Mesozoic  world.  This  group  Las  now  but  few  living 

species,  and  among 

Fig*  31(  the    genera,    Cycas 

and  Zamia  are  those 
whose  names  are 
best  known.  The 
plants  have  the  as- 
pect of  Palms ;  and 

Fig    316  a. 


CYC  ADS-  Fig.  316,  Cycas  circinalis  (x 


;  316a,leaf  of  a  living  Zamia  (x 


there  was,  therefore,  in  the  Mesozoic  forests  a  min^lincr  of 

O  iD 

palm-like  foliage  v/itli  that  cf  Coniferj  (Sprues,  Cypress,  and 
the  like).     But  the  Cycads  arc  nut  true  Palms.     They  are 


TRIASSIC   AND   JURASSIC   PERIODS. 


289 


Fig.  317. 


Gymnosperms,  like  the  Conifers  both  in  the  structure  of  the 
wood  and  in  the  fruit.  The  resemblance  to  Palms  is  mainly  in 
the  cluster  of  great  leaves  at  the  sum- 
mit, and  in  the  appearance  of  the  exte- 
rior of  the  trunk.  Fig.  316  represents, 
much  reduced,  a  modern  Cycas,  and 
31 6  a  the  leaf  of  a  living  Zamia,  one 
twentieth  the  actual  length.  The  fossil 
remains  of  Cycads  are  either  their 
trunks  or  leaves.  A  fossil  species  from 
the  Portland  dirt-bed  is  represented  in 
Fig.  317-  The  trunks  of  some  Cycads 
have  a  height  of  15  or  20  feet.  In 
one  important  respect  these  Cycads 
resemble  the  Ferns,  —  that  is,  in  the  unfolding  of  the  young 

Figs   318-322 


Stump  of  the  Cycad,  Mantellia 
(Cycadeoidea)      megalophylla 


Fig.  318,  Podozamites  lanceolatus  ;  319,  Pterophyllum  graminioides  ;  320,  Clathropteris  rec- 
tiusculus;  321,  Pecopteris  (Lepidopteris)  Stuttgartensis  ;  322,  Cyclopteris  linnaeifolia. 


290  MESOZOIC   TIME.  — REPTILIAN   AGE. 

leaf,  —  the  leaf  being  at  first  rolled  up  into  a  coil,  and  grad- 
ually unrolling  as  it  expands.  The  Cycads  thus  combine 
peculiarities  of  three  orders  of  plants,  —  Ferns,  Palms,  and 
Conifers,  —  and  are  examples,  therefore,  of  what  are  called 
comprehensive  types. 

Fossil  plants  are  common  in  the  coal-regions  of  Eichmond, 
Virginia,  and  in  North  Carolina,  and  occur  also  in  other 
localities.  Figs.  318,  319  are  parts  of  the  leaves  of  two 
species  of  Cycads,  from  North  Carolina.  Figs.  320  to  322 
represent  a  few  of  the  ferns :  Fig.  320,  a  Clathropteris,  from 
East  Hampton,  Mass. ;  Fig.  321,  a  Pecopteris,  from  Eichmond, 
Va.,  and  the  Trias  of  Europe ;  Fig.  322,  a  Cyclopteris,  from 
Eichmond,  Ya.  Large  cones  of  firs  have  also  been  found. 
Several  of  the  American  plants  are  identical  in  species  with 
those  of  the  European  Triassic,  and  a  few  nearer  to  Jurassic 
forms. 

2.  Animals, 
a.   American. 

The  American  beds  of  the  Atlantic  border  region  are  re- 
markable for  the  absence  of  true  marine  life :  all  the  species 
appear  to  be  either  those  of  brackish  water,  or  of  fresh  water, 
or  of  the  land. 

1.  Radiates  and  Mollusks.  —  In  the  beds  of  the  Atlantic 
border  Eadiates  are  unknown ;  and  the  remains  of  Mollusks 
are  of  doubtful  character.     The  Jurassic  beds  of  the  Eocky 
Mountain  region  and  its  western  borders  contain  many  spe- 
cies, and  the  Triassic  of  California  a  few. 

2.  Articulates.  —  The   shells  of  Ostracoid   Crustaceans   are 
common  in  New  Jersey,  Pennsylvania,  Virginia,  and 

North  Carolina,  but  have  not  yet  been  found  in  New 
England.  Fig.  323  represents  one  of  the  little  shells 
of  these  bivalve  species,  called  an  Esthcria.  It  was 
long  supposed  to  be  Molluscan.  The  EstJierioe  are 
brackish-water  species. 

A  few  remains  of  Insects  have  been  found,  and,  what  is  more 
remarkable,  the  tracks  of  several  species.  These  tracks  were 


TRIASSIC  AND  JURASSIC   PERIODS. 


291 


made  on  the  soft  mud,  probably  by  the  larves  of  the  Insects, 
for  certain  kinds  pass  their  larval  state  in  the  water.  Fig. 
324  represents  one  of  these  larves  found  in  shale  at  Turner's 
Falls  in  Massachusetts;  it  resembles,  according  to  Dr.  Le  Conte, 
the  larve  of  a  modern  Ephemera,  or  May-fly.  Figs.  325,  326 
are  the  tracks  of  Insects.  Pro- 
fessor Hitchcock  has  named 
nearly  30  species  of  tracks  of 
Insects  and  Crustaceans. 

3.  Vertebrates.  —  There  are 
evidences  of  the  existence  of 
Fishes,  Reptiles,  Mammals,  and 
probably  Birds.  With  the  ap- 
pearance of  the  last  two  types 
the  sub-kingdom  of  Vertebrates 
was  finally  represented  in  all  its  ARTICULATES.  —  Fig.  324 


Figs   324-326 

325 


H 

/       » 


A 
f\ 

r\ 


r* 


classes. 


mediseva  (  x  H) ;  325,  326,  Tracks  of  Insects. 


1.  The  Fislws  found  in  the  American  rocks  are  all  Ganoids, 
although  Selachian  remains  are  common  in  Europe.  Fig.  327 
represents  one  of  the  species,  reduced  one  half;  the  tail  is  half 
vertebrated.  In  other  species  of  these  rocks  it  is  not  at  all 
vertebrated,  being  like  that  of  modern  Ganoids ;  and  in  them 
this  old  paleozoic  feature  of  the  Ganoids  is  finally  lost. 

Fig.  327- 


Fig.  327,  GANOID,  Catopterus  gracilis  ( x  £) ;  a,  Scale  of  same,  natural  size. 

2.  Amphibians,  of  the  tribe  of  Labyrinthodonts  (page  257), 
appear  to  have  reached  their  greatest  size  and  numbers  in  the 
Triassic  period.  A  foreign  species  is  mentioned  on  page  300. 


292 


MESOZOIC    TIME.  — REPTILIAN    AGE. 


Footprints  of  the  Connecticut  valley  beds  appear  to  indicate 
the  existence  of  American  species.  Figs.  330,  330  a,  and  331, 
331  a  represent  tracks  of  two  of  these.  But  among  the  kinds 


Figs.  328-332. 


REPTILES.  —  Fig.  328,  Bathygnathns  borealis(X  J) ;  329,  Belodon  priscus  ;  329  a,  section 
of  same;  330,  330  «,  fore  and  hind  feet  of  Anisopus  Deweyanus  (X  1) ;  331,  331  a,  ibid,  of 
A.  gracilis  (X  !) ;  33-2,  332  a,  ibid,  of  Otozoum  Moodii  (X  is)- 

so  referred  some  were  biped  in  locomotion  ;  and  these,  accord- 
ing  to  Marsh,  were  probably  Dinosaurs,  as  described  below. 

3.  True  Reptiles.  —  1.  Dinosaurs.  —  The  Dinosaurs  were 
so  named  from  the  Greek  deivog,  terrible,  and  oavpoz,  lizard, 
some  species  being  of  great  size.  They  were  the  leading 
life  of  North  America  in  Triassic  and  Jurassic  time.  In 
the  East  they  are  known  from  the  thousands  of  footprints  left 
by  them  in  the  Connecticut  valley  and  New  Jersey,  and  to  a 
small  extent  from  bones,  and  these  chiefly  from  Pennsylvania 
and  North  Carolina;  and  in  Western  America  from  huge 
skeletons  found  in  the  Eocky  Mountain  region.  Many,  as  the 
tracks  show,  were  biped  in  locomotion,  while  others  were 
quadruped-like.  The  bipeds  were  of  two  tribes  In  one, 
the  animals  made  %-tord  Hrd-Hke  tracks,  as  in  Figs.  333, 
334 ;  in  the  other,  broad  4-toed  or  5-toed  tracks,  as  in 


TRIASSIC  AND   JURASSIC  PERIODS. 


293 


Fig.  332  a  (Fig.  332  being  the  corresponding  fore-foot). 
The  track  represented  in  Fig.  333  is  actually  eighteen  inches 
long,  and  that  of  Fig.  332  a,  twenty  inches ,  and  probably 
each  of  these  biped  Dinosaurs  stood  over  twenty  feet  high. 
Some  of  the  3-toed  tracks  are  accompanied  by  impressions  of 
fore-feet,  proving  that  the  animals  were  not  birds,  and  render- 
ing it  probable  that  none  were  so.  The  biped  march  of  these 
species  is  a  bird-like  characteristic,  and  it  is  connected  with  a 
more  or  less  bird-like  pelvis,  and  sometimes  with  hollow  bones. 
Fig.  328  represents  a  tooth  of  a  Dinosaur  from  Prince  Ed- 
ward's Island. 


Figs    333,  334. 


331 


Fig.  333,  Track  of  Brontozoum  giganteam  (X  e) ;  334,  SSlub  of  saudstoue  with  tracks  of 
Birds?  and  Reptiles  (  X  go). 

Jurassic  Dinosaurs  of  enormous  size  have  been  described 
by  Marsh  from  beds  in  Wyoming  and  Colorado.  One  named 
by  him,  Atlantosaurus,  had  the  thigh  bone  over  6  feet  long, 
and  a  length  of  body  of  probably  60  feet,  showing  a  magni- 
tude before  thought  impossible  in  a  terrestrial  animal. 

2.  Lacertians,  or  Lizard-like  spesies,  —  Fig.  329  represents  a 
tooth  from  North  Carolina  referred  to  a  Lacertian  called  Belo- 
don  prisons. 

3,  Enaliosaurs.  —  Found  in  the  Triassic  of  Nevada* 


294 


MESOZOIC  TIME.  — REPTILIAN  AGE. 


Fig.  335. 


4.  Mammals.  —  In  the  North  Carolina  Triassic  have  been 
found  two  jaw-bones  (Fig.  335)  of  a  species  of  Marsupial  — 
the  division  of  Mammals  to  which  the  modern  Opossum  of  the 
same  region  belongs.  Several  other  Marsupials  have  been  de- 
scribed by  Marsh  from  Jurassic  beds  in  Wyoming  and  Colorado. 

The  facts  prove  that  the 
land  population  of  Mesozoic 
America  included  Insect*, 
Amphibians,  Reptiles,  and 
Marsupial  Mammals;  and 
that  the  forests  which  cov- 
ered the  hills  were  mainly  composed  of  Conifers  arid  Cycads. 
Birds  may  have  been  present  also  :  for  (1)  remains  of  true 
Birds  have  been  found  in  the  Jurassic  of  Europe  ;  (2)  it  seems 
hardly  probable  that  Mammals  should  have  preceded  Birds  ; 
and  (3)  Birds,  because  terrestrial  arid  of  slender  bones,  are 
the  least  likely  of  species  to  be  preserved. 


Jaw-bone  of  Dromatherium  sylvestre. 


The  European  and  British  rocks  of  these  periods,  especially 

337  Pigs.  336-339 


RADIATES:  Fig.  336,  Prionastrsea  oblonga(aCoral)  ;  337,  Encrinus  liliiformis  (aCrinoid); 
338,  Cidaris  Blumenbacliii  (an  Echinus)  ;  339,  Spine  of  same. 


TRIASSIC  AND  JURASSIC  PERIODS. 


295 


of  the  Jurassic,  abound  in  marine  fossils,  and  afford  a  good 
idea  of  the  Mesozoic  life  of  the  ocean.  The  remains  of  ter- 
restrial life  are  also  of  great  interest,  Marsupial  Mammals 
occurring  in  the  Triassic  beds,  and  birds  in  the  Jurassic. 

1.  Radiates.  —  Polyp-corals  are  common  in  some  Jurassic 
strata :  they  are  related  to  the  modern  tribe  of  corals,  and  not 
to  the  ancient.     Fig.  336  represents  one  of  the  Oolytic  spe- 
cies.    Oinoids  are  of  many  kinds,  yet  their  number,  as  com- 
pared with  other  fossils,  is  far  less  than  in  the  preceding 
ages ;   and  they  are  accompanied  by  various   new  forms  of 
Star-fishes  and  Echini  (page   183).    Fig.  337  represents  one 
of  the  Triassic  Crinoids,  the  Lily-Encrinite,  or  Encrinus  lilii- 
f or  mis ;  Fig.  338,  an  Echinus,  from  the  Ob'lyte,  stripped  of  its 
spines ;  and  Fig.  339,  one  of  the  spines  separate. 

2.  Mollusks.  —  Brachiopods   are  few  compared  with  their 
number  in  the  Paleozoic.     The  last  species  of  the  Paleozoic 
genera,  Spirifer  and  Leptcena,  lived  in  the  early  part  of  the 


Figs.  340-343. 


340 


MOLLUSKS:  Fig.  340,  Spirifer  Walcotti ;  341,  Gryphsea  incurva  ;  342,  Trigonia  clavellata  ; 
343,  Viviparus  (Paludina)  fluviorum. 

Jurassic  period.  Fig.  340  represents  one  of  these  last  of  the 
Spirifer  group.  Lamellibraiichs  and  Gasteropods  abound  in  spe- 
cies, and  under  various  new,  and  manv  of  them  modern,  genera. 


296 


MESOZOIC  TIME.  —  REPTILIAN  AGE. 


Species  of  the  genus  Gryplicea  were  common  in  the  Lias  and 
later  Mesozoic  rocks :  they  are  related  to  the  Oyster,  but  have 
the  beak  incurved.  Fig.  341  represents  a  Liassic  species. 
Trigonia  (Fig.  342)  is  a  characteristic  genus  of  the  Mesozoic ; 
the  name  alludes  to  the  triangular  form  of  the  shell :  the 
species  figured  is  from  the  Oolyte.  Fig.  343  represents  a 
fresh- water  snail-shell,  a  very  abundant  fossil  in  the  fresh- 
water limestone  of  the  Wealden,  closely  resembling  many 
modern  species. 

But  the  most  remarkable  and  characteristic  of  all  Mesozoic 
Mollusks  were  the  Cephalopods.  This  order  passed  its  maxi- 
mum as  to  number  and  size  in  the  Mesozoic,  and  hundreds  of 
species  existed.  The  last  of  the  Paleozoic  types  of  Ortlwcerata 


Figs    344,  345. 


S44 


MOLLUSKS  :  Fig.  344,  Ammonites  Humphreysianus  ;  345,  A.  Jason. 


and  Goniatites  lived  in  the  Triassic  period.  In  the  same  pe- 
riod species  of  Ammonites,  one  of  the  most  characteristic  of 
Mesozoic  groups,  became  common ;  and,  in  the  earliest  Juras- 
sic, the  first  of  Belemnites,  another  peculiarly  Mesozoic  type, 
appeared. 

The  Ammonites  had  external  chambered  shells  like  the  Nau- 


TRIASSIC  AND  JURASSIC   PERIODS.  297 

till  (page  181)  and  Goniatites.     Two  Oolytic  species  are  repre- 
sented in  Figs.  344,  345.     One  of  them  (Fig.  345)  has  the 
side  of  the  aperture  very  much  prolonged ;  but  the  outer  mar- 
gin of  the  shell,  whether  prolonged  or  not,  is  seldom  well 
preserved.     The  partitions  (or  septa)  within 
the  shells  of  Ammonites  are  bent  back  in 
many  folds  (and  much  plaited  within  each 
fold)  at  their  junction  with  the  shell,  so  as 
to  make  deep  plaited   pockets.     The  front 
view  of  the  outer  plate,  with  the  entrances  to 
its  side-pockets,  are  seen  in  Fig.  346.     The 
fleshy  mantle  of  the  animal  descended  into 
these  pockets,  and  thus  the  animal  was  aided 
in  holding  firmly  to  its  shell.     The  siphuncle 
in  the  Ammonites  is  dorsal.     The  Paleozoic 
Goniatites  were  of  the  Ammonite  family,  but     Ammonites  tornatus. 
the  pockets  were  much  more  simple,  the  flex- 
ures of  the  margins  of  the  partitions  being  without  plications. 

The  fossil  Belcmnite  is  the  internal  bone  of  a  kind  of  Ce- 
phalopod,  analogous  to  the  pen  or  internal  bone  (or  osselet)  of 
a  Sepia,  or  Cuttle-fish  (see  Fig.  351).  It  is  a  thick,  heavy  fos- 
sil, of  the  forms  in  Figs.  347,  348,  having  a  conical  cavity 
at  the  upper  end.  The  fossils  are  more  or  less  broken  at  this 
extremity ;  when  entire,  the  margin  of  the  aperture  is  elon- 
gated into  a  thin  edge,  and  sometimes,  on  one  side,  into  a  thin 
plate  of  the  form  in  Fig.  349.  The  animal  had  an  ink-bag 
like  the  modern  Sepia ;  and  ink  from  these  ancient  Cephalo- 
pods  has  been  used  in  sketching  their  fossil  remains.  Fig. 
350  represents  one  of  the  ink-bags  of  the  Jurassic  Cephalo- 
pods.  Fig.  351  is  another  related  Cephalopod,  showing  some- 
thing of  the  form  of  the  animal,  and  also  the  ink-bag  in  place. 

3.  Articulates.  —  The  Articulates  included  various  shrimps, 
or  craw-fishes  (Fig.  352,  a  Triassic  species),  Crabs,  and  Te- 
tradecapod  (or  14-footed)  Crustaceans  (Fig.  353,  representing 
a  species  something  like  the  modern  Sow-bug),  but  no  Tri- 
lobites  ;  also  Spiders  (Fig.  354),  and  species  of  many  of  the 


298 


MESOZOIC   TIME.  — REPTILIAN   AGE. 


orders  of  Insects.  Fig.  355  is  a  Libeliula,  or  Dragon-fly,  of 
the  Jurassic  period,  from  Solenhofen  ;  and  Fig.  356,  the  wing- 
case  of  a  beetle,  from  the  Stonesfield  Oolyte. 


Figs.  347-351. 


MOLLUSKS  :  Fig.  347,  Belemnites  clavatus  ;  348,  B.  paxillosus  ;  348  «,  Outline  of  section 
of  same,  near  extremity  ;  319,  View,  reduced,  of  the  complete  osselet  of  a  Belemnite ;  350, 
Fossil  ink-bags  of  a  Cephalopod  ;  351,  Acanthoteuthi.s  antiquus. 

4.  Vertebrates.  —  The  Fishes  were  chiefly  Ganoids  or  Sela- 
chians. In  the  Triassic  beds  of  Europe,  as  in  America,  oc- 
curred the  last  species  of  the  vertebrated-tailed  Ganoids,  and 
the^rs^  of  those  having  the  tail  not  vertebrated.  Fig.  357 
represents  one  of  the  latter  kind  from  the  Lias.  Among  the 


TRIASSIC  AND  JURASSIC  PERIODS. 


299 


SJiarks  (or  Selachians)  the  Cestraciont  tribe,  one  of  the  most 
ancient,  characterized  by  a  pavement  of  grinding  teetli  (page 


Figs    352-356. 


ARTICULATES  :  Fig.  352,  Pempliix  Sueurii ;  353,  Archieoniscus  Brodiei  ;  354,  Palpipes 
prisons  ;  355,  Libellula  ;  356,  Wing-case  of  a  Buprestis. 

178),  still  continued,  and  was  very  numerously  represented. 
There  were  also,  in  the  Jurassic  beds,  Sharks  having  sharp- 


Fig.  357 


VERTEBRATE :  Fig.  357,  Restored  figure  of  /Echmodus  (Tetragonolepis)  from  the  Lias 
(x  J) ;  367  a,  Scales  of  same. 

edged  teeth  like  those  of  the  tribe  of  Sharks  that  inhabits 
modern  waters. 

The  genus  Ccratodus,  represented  by  species  in  the  Trias, 


300  MESOZOIC   TIME.  —  REPTILIAN   AGE. 

has  living  species  in  Australia ;  and  they  are  Ganoids,  related 
to  the  modern  Dipnoans,  or  fishes  that,  like  the  Lepidosiren, 
have  both  gills  and  lungs. 

Amphibians  were  common  in  the  European  Trias,  as  in  the 
American,  and  some  were  of  gigantic  size. 

Figs    358-360. 


VERTEBRATES:  Fig.  358,  Skull  of  Mastodonsaurus  giganteus  ( x  i);  359,  Tooth  of  same 
(x  £);  360,  Footprints  of  Cheriotherium  (x  y?). 

Among  the  Triassic  Amphibians,  one  frog-like  Labyrintlio- 
dont  had  a  skull  over  2  feet  long,  of  the  form  shown  in  Fig. 
358 ;  its  mouth  was  set  round  with  teeth  3  inches  long  (Fig. 
359),  and  the  body  was  covered  with  scales.  The  specimen 
here  figured  was  found  iu  Saxony.  Tt  is  probable  that  some 
of  the  American  Reptilian  species  whose  tracks  are  so  com- 
mon in  the  Connecticut  Valley  were  of  this  type.  Fig.  360  is 
a  reduced  view  of  hand-like  tracks,  from  the  same  locality  as 
the  above,  supposed  to  have  been  made  by  an  animal  of  the 
same  species.  The  frogs  of  the  present  day  are  feeble  and 
diminutive  compared  with  the  Triassic  Amphibians. 

The  True  Reptiles  included  species  for  each  of  the  elements> 
—  the  water,  the  earth,  the  air. 

Among  them  there  were,  first,  Swimming  Reptiles,  —  called 
Enaliosaurs  because  they  belonged  especially  to  the  sea  (from 
the  Greek  eVaXto?,  of  the  sea,  and  aavpos,  lizard) ;  they  prob- 


TRIASSIC   AND  JURASSIC   PERIODS. 


301 


ably  existed  in  the  Carboniferous  age  (page  258),  but  became 
numerous  and  of  great  size  in  the  Middle  Mesozoic.  They 
had  paddles  like  Whales,  and  thus  were  well  fitted  for  marine 
life.  The  most  common  kinds  were  the  Ichthyosaurs  and  Ple- 
siosaurs. 

Figs.  361-365 


VEHTE3AATES  :  Fi-.  361,  Ichthyosaurus  communis  (X  ifo);  362,  Head  of  same  (X  jfo)  5 
3u3  o,  303  b,  View  and  section  of  vertebra  of  same  (X  i) ;  364,  Tooth  of  same,  natural 
size  :  3oa,  Plesiosaurus  dolicliodeirus  (x  g^)  >  365  a>  365  b>  View  and  section  of  vertebra 
of  same. 

The  Ichthyosaurs  (Fig.  361)  had  a  short  neck,  a  long  and 
large  head,  enormous  eyes,  and  thin,  doubly-concave,  and 
therefore  fish-like,  vertebrae.  The  name  is  from  the  Greek 
Ix0vs>  fi*h>  an(i  travpos,  lizbrd.  Fig.  362  represents  the  head 
of  an  Iclithyosaur,  one  thirtieth  the  natural  length,  showing 
the  large  size  of  the  eye  and  the  great  number  of  the  teeth. 
Fig.  363  b  is  one  of  the  vertebrtc,  reduced,  and  Fig.  363  «,  a 
transverse  section  of  the  same,  exhibiting  the  fact  that  both 
surfaces  are  deaply  concave,  nearly  as  in  fishes  ;  Fig.  364  is 
one  of  the  teeth,  natural  size.  Some  of  the  Ichthyosaurs  were 
30  feet  long. 


302  MESOZOIC   TIME.  —  REPTILIAN   AGE. 


The  Plesiosaurs  (named  from  the  Greek  TrXrja-ios,  near,  and 
craiJpo?,  because  not  quite  like  a  Saurian),  one  of  which  is  rep- 
sented  very  much  reduced  in  Fig.  365,  had  a  long  snake-like 
neck,  a  comparatively  short  body,  and  a  small  head.  Fig. 
365  a  represents  one  of  the  vertebrae,  and  365  b,  a  section 
of  the  same  ;  it  is  doubly  concave,  but  less  so,  and  much 
thicker,  than  in  the  Iclithyosaurs.  Some  species  of  Plesiosaur 
were  25  to  30  feet  long.  Another  related  Eeptile,  called  a 
Pliosaur,  was  30  to  40  feet  long.  Remains  of  more  than  50 
species  of  Enaliosaurs  have  been  found  in  the  Jurassic  rocks. 

Besides  these  swimming  Saurians,  there  Avere  numerous 
species  of  Lacertians  (Lizards)  and  Crocodilians  10  to  50  feet 
long,  and  Dinosaurs,  the  bulkiest  and  highest  in  rank  of  the 
Saurians,  25  to  60  feet  long. 

To  the  group  of  Dinosaurs  belongs  the  Iguanodon,  of  the 
Wealden  beds,  first  made  known  by  Dr.  Mantell,  whose  body 
was  28  to  30  feet  long,  and  which  stood  high  above  the 
ground  quadruped-like,  the  femur,  or  thigh-bone,  alone  being 
nearly  3  feet  long.  The  hind  feet  were  three-toed  like  those 
of  birds.  Its  habits  are  supposed  to  have  been  like  those  of 
the  ancient  sloth-like  animal  called  a  Megatherium  (page  365), 
—  the  animal  grazing  on  the  trees  along  the  borders  of  the 
marshes,  estuaries,  or  streams  in  or  about  which  it  lived,  and 
able  to  lift  its  body  on  its  hind  legs  for  this  purpose.  It  had 
teeth  li*ke  the  modern  Iguana,  (and  hence  the  name,  from 
Iguana,  and  the  Greek  o8ou?,  tootJi),  but  it  had  proportionately 
a  much  shorter  tail.  The  Megalosaur  was  another  of  the 
gigantic  Dinosaurs  of  the  later  part  of  the  Jurassic  period  ; 
it  was  a  terrestrial  carnivorous  Saurian  about  30  feet  in  length, 
and  was  better  fitted  in  its  limbs  for  raising  its  body  toward 
an  erect  posture.  The  three-toed  American  Reptiles,  whose 
tracks  are  described  on  page  293,  are  those  of  other  Dinosaurs  ; 
and  these  had  the  habit  of  bipeds.  Many  points  in  the 
structure  of  the  limbs  and  pelvis  of  the  Dinosaurs  are  similar 
to  those  of  birds. 

Reptiles  adapted  for  the  air  —  that  is,  for  flying  —  are 


TRIASSIC  AND  JURASSIC  PERIODS.  303 

designated  Pterosaurs,  from  the  Greek  Trrepov,  winy,  and 
aavpos.  The  most  common  genus  is  called  Pterodactylus. 
The  general  form  of  a  Pterodactyl  is  shown  in  Fig.  366.  The 
bones  of  one  of  the  fingers  are  greatly  elongated,  for  the  purpose 

Fig.  366. 


VERTEBRATE.  —  Pterodactylus  crassirostris  (x  })• 

of  supporting  an  expanded  membrane,  so  as  to  make  it  serve 
(like  an  analogous  arrangement  in  bats)  for  flying.  The  name 
Pterodactyl  is  from  the  Greek  irrepov,  wing,  and  $aKTv\o$, 
finger.  The  Jurassic  Pterodactyls  were  mostly  small,  and 
probably  had  the  habits  of  bats ;  the  largest  had  a  spread  of 
wing  of  about  10  feet.  Unlike  our  common  birds,  they  had 
a  mouth  full  of  teeth,  and  no  feathers.  As  Bats  are  flying 
Mammals,  so  the  Pterosaurs  are  simply  flying  Reptiles,  and 
have  little  resemblance  to  birds  iu  structure,  except  that 
their  bones  are  hollow,  and  adapted  in  form  for  the  bird- 
like  characteristic  of  flying. 

Besides  the  kinds  of  Eeptiles  already  mentioned,  there  were 
Turtles  in  the  Jurassic  period;  but,  according  to  present 
knowledge,  the  world  contained  no  true  Snakes. 

Coprolites  (or  fossil  excrements)  of  both  Reptiles  and  Fishes 
are  common  in  the  bone- beds.  When  cut  and  polished  they 


304  MESOZOIC  TIME.  —  REPTILIAN  AGE, 

Fig.  367 


TERTEBRATE.  -  The  binl,  Archaopteryx  macrura. 


TRIASSIC   AND   JURASSIC   PERIODS. 


305 


have  a  degree  of  beauty  sufficient  to  give  them  some  value  in 
jewelry. 

Eemains  of  Birds  have  been  found  in  the  quarries  of  Solen- 
hofen  (page  287).  They  have  revealed  the  fact  that  some  at 
least  of  the  Mesozoic  Birds  (and  of  America,  beyond  question, 
as  well  as  Europe)  were  reptilian  in  some  of  their  characters. 
The  skeleton  found  (Fig.  367)  shows  that  the  Birds  had  long 
reptile-like  tails  consisting  of  many  vertebrae,  and  finger-like 
claws  on  the  fore  limb  or  wing,  like  those  of  the  Pterodactyl 
and  Bat,  fitting  them  evidently  for  clinging.  But,  while 
thus  reptilian  in  some  points  of  structure,  they  were  actually 
Birds,  being  feathered  animals,  and  having  the  expanse  of 
the  wing  made,  not  by  an  expanded  membrane  as  in  the 
Pterodactyl,  but  by  long  quill-feathers.  The  tail-quills  were 

Figs    368,  369. 


VERTEBRATES.  —  Fig.  368,   Amphitherium   Broderipii    (x2);    369,   PKascolotherium 
Bucklandi  (x  2). 

arranged  in  a  row  either  side  of  the  long  tail.     Th<e  feet  were 
like  those  of  birds. 

Remains  of  Mammals  occur  in  the  Upper  Trias  (or  base 
of  the  Lias)  of  Germany,  in  the  Lower  Oolyte  deposit  at 
Stonesfield,  England,  and  in  the  Middle  Purbeck  beds  of  the 
Upper  Oolyte  (page  287).  Nearly  20  species  have  been  made 
out,  14  of  them  from  relics  in  the  Middle  Purbeck.  The 
larger  part,  if  not  all,  are  Marsupials.  Figs.  368,  369  repre- 
sent the  jaws  of  two  species  from  Stonesfield,  magnified  twice 
the  natural  size. 

20 


306  MESOZOIC  TIME.  —  EEPTILIAN  AGE. 

As  Marsupials  are  semi-oviparous  Mammals,  and  therefore 
are  intermediate  between  ordinary  Mammals  and  the  inferior 
and  oviparous  Vertebrates  (page  176),  it  follows  that  both  the 
Birds  and  Mammals  of  the  Mesozoic  were  in  part,  at  least., 
comprehensive  or  intermediate  types,  and  partook  of  reptilian 
features  in  the  Eeptilian  age. 

3.    General  Observations. 

1.  American  Geography.  —  The  Triassico-Jurassic  sand- 
stones and  shales  of  the  Atlantic  border  region  are  sedimen- 
tary beds ;  consequently,  the  long  narrow  ranges  of  country 
in  which  they  were  formed  were  occupied  at  the  time  more  or 
less  completely  by  water. 

The  absence  of  true  marine  fossils  has  been  remarked  upon 
as  proving  that  this  water  was  either  brackish  or  fresh ;  and 
hence  the  areas  were  estuaries  or  deep  bays  running  far  into 
the  land. 

There  was  probably  an  abundance  of  marine  life  in  the 
ocean,  if  we  may  judge  from  its  diversity  on  the  other  side 
of  the  Atlantic ;  but  the  sea-coast  of  the  era  must  have  been 
outside  of  the  present  one,  so  that  any  true  marine  or  sea-coast 
deposits  that  were  made  are  now  submerged.  The  present 
sea-border  is  shallow  for  a  distance  of  80  miles  from  the  New 
Jersey  coast,  the  depth  of  water  at  this  distance  out  being 
but  600  feet.  (See  map,  page  12.) 

As  all  the  depressions  or  valleys  occupied  by  the  estuaries 
are  parallel  with  the  Appalachians  (page  285),  and  since  the  era 
of  the  formations  was  that  next  following  the  origin  of  these 
mountains,  the  depressions  were  probably  made  at  the  time 
the  Appalachian  foldings  were  in  progress,  or  are  great  valleys 
or  depressions  then  left  in  the  surface. 

The  level  of  the  several  sandstone  areas  above  the  ocean 
proves  that  the  land  at  the  time  was  not  far  from  its  present 
elevation,  and  therefore  that  the  Appalachians  had  probably 
nearly  their  present  height. 

The   deposits   contain   footprints,  ripple-marks,  rain-drop 


TRIASSIC   AND  JURASSIC   PERIODS.  307 

impressions,  and  other  evidences,  on  many  of  the  layers,  that 
they  were  formed  partly  in  shallow  waters,  and  partly  as 
sand-flats,  or  emerging  marshes  and  shores,  over  which  reptiles 
and  birds  might  have  walked  or  waded.  If,  then,  they  are 
several  thousands  of  feet  thick,  there  must  have  been  a 
progressing  subsidence  of  the  valley-depressions,  —  that  is,  a 
sinking  must  have  been  going  on.  It  is  hence  apparent  that 
oscillations  of  level,  like  those  that  characterized  the  Appala- 
chian region  before  and  during  the  Appalachian  revolution, 
were  in  progress.  Two  effects  of  this  subsidence  occurred : 
(1)  The  sandstone  beds  were  more  or  less  faulted  and  tilted, 
those  of  the  Connecticut  Valley  receiving  a  dip  to  the  eastward, 
or  southeastward,  those  of  New  Jersey  and  Pennsylvania  to 
the  northwestward.  (2)  In  the  sinking  of  the  valley-depres- 
sion, an  increasing  strain  was  produced  in  the  earth's  crystal- 
line crust  beneath,  which  finally  became  so  great  that  the  crust 
broke,  fissures  opened,  and  liquid  rock  came  up.  The  dikes 
and  ridges  of  trap  are  this  liquid  rock  solidified  by  cooling. 
The  existence  of  the  dikes,  and  their  parallelism  to  the  general 
course  of  the  valley-depressions,  prove  —  (1)  the  fact  of  the 
fractures ;  (2)  their  resulting  from  the  same  cause  which  pro- 
duced the  sinking ;  and  (3)  the  fact  of  the  igneous  ejections. 
The  earth's  crust  along  the  Connecticut  Valley  was  thus  a 
scene  of  igneous  operations  for  more  than  100  miles,  and 
through  a  vast  number  of  opened  fissures.  All  the  Trias- 
sico-Jurassic  areas  from  Nova  Scotia  to  Southern  North  Caro- 
lina, a  distance  of  1,000  miles,  were  similarly  broken  through 
and  invaded  by  trap  ejections.  The  Palisades  of  the  Hudson 
date  from  this  period,  —  probably  the  middle  or  later  part  of 
the  Jurassic  period. 

The  Western  Interior  or  Rocky  Mountain  region  had  been 
mostly  submerged  during  the  Carboniferous  age,  as  shown  by 
the  fact  that  limestones  were  forming  there  in  the  Coal-Meas- 
ure period,  and  fossiliferous  sandstones  in  the  Permian.  The 
Triassic  sandstone  there  proves,  by  its  nature,  its  gypsum  in 
many  places,  and  the  paucity  of  fossils,  that,  by  some  change, 


308  MESOZOIC   TIME.  — REPTILIAN  AGE. 

the  region  had  become  mostly  an  interior  shallow  salt  sea, 
shut  off  to  a  great  extent  from  the  ocean.  Such  a  sea  would 
have  been  made  too  fresh  for  marine  life  in  the  rainy  season, 
and  probably  too  salt  for  almost  all  life  in  the  hot  season. 
Hence,  life  would  have  been  nearly  or  quite  absent.  The 
salt  waters  by  evaporation  would  have  furnished  gypsum  to 
the  beds,  as  happens  now  sometimes  from  sea-water.  It  fol- 
lows, then,  from  the  beds  of  the  Atlantic  border  as  well  as 
those  of  the  Western  Interior,  that  the  continent  during  the 
era  of  these  Mesozoic  beds  was  to  a  less  extent  submerged 
than  in  the  greater  part  of  the  Paleozoic  ages  and  the  follow- 
ing portion  of  the  Mesozoic.  The  fossiliferous  Jurassic  beds 
overlying  the  western  Triassic  show  that,  before  the  Jurassic 
period  had  closed,  the  sea  had  again  free  access  over  it  and 
oceanic  life  was  abundant. 

2.  Foreign  Geography.  —  The  nature  of  the  Triassic  beds 
of  Britain  and  Europe  shows  that  there  were  large  shallow  in- 
terior seas  also  on  the  eastern  .jicie  of  the  Atlantic.  The  salt- 
deposits  in  the  beds,  the  paucity  of  fossils  in  the  most  of  the 
strata,  and  the  prevalence  of  maiiytes,  indicate  the  same  coa- 
ditions  as  existed  in  New  York  during  the  formation  of  the 
Saliferous  beds  of  the  Upper  Silurian  (see  page  100),  and 
somewhat  similar  to  those  in  which  the  Eocky  Mountain 
Gypsiferous  formation  originated.  The  limestone  that  inter- 
vened along  the  Rhine,  between  the  two  formations  of  sand- 
stone and  marlytes,  shows  an  interval  of  more  open  sea ;  yet 
the  impurity  of  the  limestone  suggests  that  the  ocean  had  not 
full  sweep  over  the  region. 

The  beds  of  the  Jurassic  period  are  almost  all  of  them 
evidence,  both  from  their  constitution  and  their  abundant 
marine  life,  that  the  free  ocean  again  had  sway  over  large 
portions  of  the  Continental  area.  Its  limits  in  Great  Britain, 
however,  became  more  contracted  as  the  period  passed,  and 
toward  its  close  fresh- water  and  terrestrial  beds  were  forming 
in  some  places  that  had  earlier  in  the  period  been  under  salt 
water. 


TRIASSIC  AND  JURASSIC   PERIODS.  309 

3.  Climate.  —  The  Jurassic  coral-reefs  of  Britain  indicate 
that  England  then  lay  within  the  sub-tropical  oceanic  zone. 
This  zone  now  has  the  parallel  of  27°  to  28°  as,  in  general,  its 
outer  limit  (lying  mostly  between  20°  and  27°) ;  and,  conse- 
quently, its  Jurassic  limit,  if  including  England,  reached  twice 
as  far  toward  the  pole  as  now.  It  is  possible,  however,  that 
the  line  would  have  run  along  the  British  Channel,  were  it 
not  for  the  Gulf  Stream  of  the  era,  which  carried  the  sub- 
tropical temperature  northeastward  through  the  British  seas, 
as  it  now  does  to  Bermuda,  in  latitude  34°. 

The  following  are  other  facts  of  similar  import.  In  Arctic 
America  species  of  shells  allied  to  those  of  Europe  and  tropi- 
cal South  America  occur  in  latitudes  60°  to  77°  1C';  and  one 
species  of  Belewinite  and  one  of  Ammonite  are  said  to  be  iden- 
tical with  species  occurring  in  these  two  remote  and  now 
widely  different  regions.  If  not  absolutely  identical,  the  evi- 
dence from  them  as  to  oceanic  temperature  is  nearly  the 
same.  Moreover,  on  Exmouth  Island,  in  77°  16'  N.,  remains 
of  an  Ichthyosaur  have  been  found,  and  in  76°  22'  N.,  on 
Bathurst  Island,  bones  of  other  large  Jurassic  Eeptiles  (Teleo- 
saurs).  It  is  probable,  therefore,  that  a  warm-temperate 
oceanic  zone  covered  the  Arctic  to  the  parallel  of  78°,  if  not 
beyond.  No  large  living  reptiles  exist  outside  of  the  warm- 
temperate  zone. 

DISTURBANCES   CLOSING   THE  JURASSIC   PERIOD. 

After  the  Jurassic  period,  or  near  its  close,  the  lofty  ranges 
of  the  Sierra  Nevada,  on  the  eastern  boundary  of  California 
and  the  western  of  the  Great  Plateau  or  Basin  were  made  ; 
and  probably  also  the  Huinboldt  Eange,  above  12,000  feet  in 
height,  and  other  ranges  over  the  dry  plateau  between  the 
Sierra  Nevada  and  the  Wahsatch  Eange.  Triassic  and  Ju- 
rassic fossils  have  been  found  in  the  rocks  of  the  Sierra  Ne- 
vada, while  Cretaceous  fossiliferous  beds  lie  unconformably 
over  the  upturned  strata  of  the  mountains;  the  latter  fact 


310  MESOZOIC   TIME.  —  REPTILIAN  AQE. 

proving  that  the  mountain-making  occurred  before  the  Creta- 
ceous era,  and  the  former,  that  it  took  place  after  the  Juras- 
sic era.  The  ejections  of  trap  in  the  Triassico-Jurassic  areas 
of  the  Atlantic  border  occurred  previous  to  the  Cretaceous 
period,  and  perhaps  contemporaneously  with  the  making  of 
the  mountains  on  the  Pacific  border. 


2.  Cretaceous  Period. 

General  characteristics,  —  The  Cretaceous,  while  the  closing 
period  of  Mesozoic  time,  was  also,  in  some  respects,  a  tran- 
sition era  between  the  Mesozoic  and  Cenozoic.  During  its 
progress,  as  is  explained  beyond,  occurred  the  decline,  and,  at 
its  close,  the  extinction,  of  a  large  number  of  the  tribes  of  the 
mediaeval  world,  while,  at  the  same  time,  there  appeared  in 
its  course  other  tribes  eminently  characteristic  of  the  modern 
world.  Among  the  modernizing  features,  the  most  prominent 
are  the  Palms  and  Angiosperms  among  plants,  and  the  Teliosts 
among  fishes. 

The  Palms  and  Angiosperms  include  nearly  all  the  fruit- 
trees  of  the  world,  and  constitute  far  the  larger  part  of  mod- 
ern forests.  The  Conifers  and  Cycads,  wherever  they  now 
occur  near  groves  of  Angiosperms,  exhibit  the  contrast  be- 
tween the  mediaeval  foliage  and  that  of  the  present  age  The 
Teliosts  (page  176)  embrace  nearly  all  modern  fishes  excepting 
those  of  the  order  of  Sharks,  or  Selachians.  Their  prevalence 
was  as  great  a  change  for  the  waters  as  the  new  tribes  of 
plants  for  the  land. 

I.    Rocks:   Kinds  and  Distribution. 

In  North  America,  the  Cretaceous  formation  borders  the 
continent  on  the  Atlantic  side,  south  of  New  York,  and  along 
the  north  and  west  sides  of  the  Gulf  of  Mexico  ;  besides,  it 
spreads  up  the  Mississippi  Valley  to  the  mouth  of  the  Ohio ; 
aod,  more  to  the  westward,  from  Texas,  northward,  over  the 
slopes  of  the  Rocky  Mountains,  being  now  at  a  height  in  some 


CRETACEOUS   PERIOD.  311 

places  of  10,000  to  12,000  feet  above  the  sea.  Its  beds  are 
exposed  to  view  in  New  Jersey  and  iri  some  portions  of  the 
more  southern  Atlantic  States,  though  mostly  covered  by  the 
Tertiary.  They  are  largely  displayed  through  Alabama  and 
Mississippi,  and  cover  a  great  area  west  of  the  Mississippi. 
(See  map,  page  195.)  In  the  Eocky  Mountain  region  they 
occur  east  of  the  Wahsatch,  and  south  in  Colorado,  New 
Mexico,  and  beyond;  also  west  of  the  Sierra  Nevada  iu 
California  of  great  thickness.  In  Colorado  and  New  Mexico, 
and  on  Vancouver's  Island,  there  are  valuable  beds  of  brown 
coal  (sometimes  called  lignite)  in  the  Cretaceous  formation. 
The  coal-beds  of  Wyoming  and  Utah,  near  the  Central 
Pacific  Eailroad,  and  part  of  those  to  the  south,  are  made 
Cretaceous  by  some  geologists,  and  by  others,  Tertiary. 

In  England  the  formation  occupies  a  region  just  east  of 
the  Jurassic,  stretching  from  Dorset  on  the  British  Channel 
eastward,  and  also  northeastward  to  Norfolk,  on  the  German 
Ocean,  and  continuing  near  the  borders  of  this  ocean,  still 
farther  north,  beyond  Flamborough  Head :  it  is  numbered  9 
on  the  map,  page  244.  Cretaceous  rocks  occur  also  in  North- 
ern and  Southern  France,  and  many  other  parts  of  Europe, 
covering  much  of  the  territory  between  Ireland  and  the 
Crimea,  1,140  miles  in  breadth,  and,  between  the  south  of 
Sweden  and  south  of  Bordeaux,  840  miles. 

Among  the  rocks  there  are  the  following  kinds :  the  soft 
variety  of  limestone  called  chalk ;  hard  limestones ;  ordinary 
hard  sandstones  ;  shales  and  conglomerates  like  those  of  other 
ages  ;  but,  more  common  than  these,  soft  sand-beds,  clay-beds, 
and  shell-beds,  so  imperfectly  consolidated  that  they  may  be 
turned  up  with  a  pick. 

Many  of  the  sand-beds  or  sandstones  have  a  dark  green 
color,  and  are  called  (jrcm-sand.  The  green  color  is  owing  to 
the  presence  of  dark  green  grains  which  occur  mixed  with 
more  or  less  of  common  sand.  They  are  a  hydrous  silicate  of 
iron  and  potash.  This  green-sand  is  often  used  for  fertilizing 
land,  and  when  so  used  it  is  called  marl ;  it  is  extensively 
quarried  for  this  purpose  in  New  Jersey, 


312  MESOZOIC  TIME.  —  REPTILIAN  AGE. 

Chalk-beds  are  the  source  of  flint.  The  flint  is  distributed 
through  the  chalk  iu  layers,  these  layers  being  made  up  of 
nodules  of  flint,  or  masses  of  irregular  forms.  Although  often 
of  rounded  forms,  they  are  not  water-worn  stones  of  foreign 
origin,  but  were  formed  in  place,  like  the  Jiornstone  in  the 
Corniferous  limestone  of  New  York  (page  229). 

Chalk  constitutes  a  large  proportion  of  the  Cretaceous  for- 
mation in  England  and  some  parts  of  Europe.  It  occurs  in  the 
Cretaceous  of  Western  Kansas,  but  not  on  the  Atlantic  border. 

The  succession  of  beds  in  England  is  as  follows :  1.  The 
Lower  Cretaceous,  consisting  largely  of  the  Green-sand  and 
other  arenaceous  beds,  called  collectively  the  Lower  Green- 
sand;  2.  The  Middle  Cretaceous,  containing  the  Upper  Green- 
sand  and  some  other  beds ;  3.  The  Upper  Cretaceous,  compris- 
ing the  Chalk-beds,  the  lower  part  of  which  is  without  flints. 

The  Cretaceous  beds  in  North  America  consist  of  layers  of 
^Green-sand,  thick  sand-beds  of  other  kinds,  clays,  shell-beds, 
and,  in  some  places  in  the  States  bordering  on  the  Mexican 
Gulf  (especially  in  Texas),  limestone.  The  thickness  of  the 
formation  in  NewT  Jersey  is  400  to  500  feet ;  in  Alabama, 
2,000  feet ;  in  Texas  about  800,  nearly  all  of  it  compact  lime- 
stone ;  in  the  region  of  the  Upper  Missouri,  2,000  to  2,500 
feet ;  east  of  the  Wahsatch,  9,000  feet  or  more. 

2.    Life. 

1.  Plants. 

The  first  of  Angiosperms  and  of  Palms,  as  already  stated, 
$ate  from  the  Cretaceous  period.  Leaves  of  a  few  American 
species  of  the  former  are  represented  in  Figs.  370  -  373 ;  Fig. 
,')71,  of  a  species  of  Sassafras ;  Fig.  372,  a  Liriodendron ;  and 
Fig.  373,  a  Willow ;  and  with  these  occur  leaves  of  Oak,  Dog- 
wood, Beech,  Poplar,  etc. 

Besides  these  highest  of  plants,  there  were  also  Conifers, 
Ferns,  and  Sea-weeds,  as  in  former  time,  with  some  Cycads. 
The  microscopic  Algse  called  Diatoms  (page  187),  which  make 


CRETACEOUS   PERIOD. 


313 


siliceous  shells,  and  others  called  Desmids  (page  187),  which 
consist  of  one  or  a  few  simple  green  cellules,  were  very  abun- 
dant. Both  occur  fossil  in  flint ;  and  a  species  of  the  latter 


:570 


Figs.  370-373. 


Fig.  370,  Leguminosites  Mareouanus;  371,  Sassafras  Cretaceum  ;  372,  Lir.ndendron  Meekii; 
373,  Salix  Meekii. 

is  very  similar  to  one  from  the  Devonian  hornstone  figured 
on  page  234  (Fig.  241).  The  Diatoms  are  believed  to  have 
contributed  part  of  the  silica  of  which  the  flint  is  formed. 

2.    Animals. 

1.  Protozoans.  —  The  simplest  of  animals,  Rliizopods,  of  the 
group  of  Protozoans  (page  185\  were  of  great  geological  im- 
portance in  the  Cretaceous  period ;  for  the  Chalk  is  supposed 
to  be  made  mostly  of  their  minute  calcareous  shells.  The 
powdered  chalk  is  often  found  to  contain  large  numbers  of 
these  shells,  the  great  majority  of  which  do  not  exceed  a 


314 


MESOZOIC    TIME.  —  REPTILIAN   AGE. 


Fig.  374.  —  Euplectella  specioea,  or  Glass  Sponge, 


CRETACEOUS   PERIOD. 


315 


pin's  head  in  size.  A  few  of  the  forms  are  represented  in 
Figs.  375  to  379,  all  very  much  enlarged,  except  379,  which 
is  natural  size.  A  very  common  kind  resembles  Fig.  83,  (page 


Figs.  375-379- 


879 


RHIZOPODS :  Fig.    375,  Lituola  nautiloidea  ;  376,   Flabellina  rugosa  ,    377,  Chrysalidina 
gnulata  ;  378,  Cimeolina  pavonia  ;  379,  Orbitolina  Texana. 

66),  and  is  called  a  Rotalia.    Fig.  379  represents  a  large  disk- 
shaped  species,  called  an  Orbitolina,  from  Texas. 

Besides  the  above  Protozoans,  Sponges  were  also  very 
abundant,  and  their  siliceous  spicules  (page  185)  were  another 
important  source  of  the  silica  of  the 
flints.  Some  of  the  Sponges,  both 
of  the  Cretaceous  era  and  of  mod- 
ern time  in  the  deeper  seas,  consist 
wholly,  or  nearly  so,  of  silica.  One 
of  the  modern  species,  from  deep 
water  in  the  Indian  Ocean,  is  rep- 
resented in  Fig.  374.  It  consists  of 
a  delicate  network  of  fibres  of  silica, 
and  looks  as  if  made  of  spun  glass. 
The  Ventriculites  were  large  Creta- 
ceous sponges  of  similar  character,  having  an  inverted  conical 
shape.  Fig.  380  represents  another  kind  which  was  prob- 
ably siliceous. 

2.  Radiates.  —  Mollusks.  —  Corals  and  Echini  were  Common 
among  Eacliates.  Mollusks  abounded,  both  of  the  Ammonite 
and  Belemnite  types,  besides  others  of  genera  not  peculiar  to 
the  Mesozoic.  Many  of  the  genera  are  represented  in  mod- 
ern seas. 


SPONGE.  —  Siphonia  lobata. 


316  MESOZOIC   TIME.  —  REPTILIAN   AGE. 

Figs.  391-393  are  of  some  of  the  most  characteristic  La- 
in ellibranchs  from  the  American  Cretaceous ;  Fig,  391,  an 
Exogyra ;  Fig.  392,  an  Inoceramus  ;  Figs.  393,  394,  species  of 
Gryphcea, — genera  now  extinct.  Figs.  395,  396,  represent 
shells  of  Gasteropods,  and  397  to  401,  Cephalopoda,  —  all 
American  except  399 ;  Fig.  397,  an  upper  front  view  of  an 
Ammonite,  showing  the  pockets  along  the  sides  of  one  of  the 
partitions ;  Fig.  397  a,  a  reduced  view  of  the  same  Ammonite 
in  profile ;  Figs.  398  to  400,  three  species  of  the  Ammonite 
family,  but  not  true  Ammonites,  —  one,  Fig.  398,  being  called 
a  ScapMtes  (from  the  Latin  scapha,  a  skiff  \  resembling  an 

Figs.  391-394 


JVIOLLUSKS :  Fig,  391,  Exogyra  costata  ;  392,  Inoceramus  problematicus  ;  393,  Gryphseo 
vesicularis ;   394,  G.  Pitched. 

Ammonite  with  the  shell  partly  uncoiled,  and  thus  made 
somewhat  to  resemble  a  boat ;  Fig.  399,  a  Turrilites,  or  tur- 
reted  Ammonite,  an  anomaly  in  the  family,  as  the  species  are 
almost  all  coiled  in  a  plane ;  Fig.  400,  a  Baculites,  or  straight 
Ammonite,  so  named  from  the  Latin  bacculum,  a  walking-stick. 
Some  of  the  Ammonites  of  the  Cretaceous  period  are  3  to  4 
feet  in  diameter. 

Fig.  401  represents  a  common  New  Jersey  Belemnite. 


CRETACEOUS  PERIOD. 


317 


3.  Vertebrates,  —  Among  Vertebrates  there  were  great  num- 
bers of  the  Tcliost  or  Osseous  Fishes,  —  fishes  allied  to  the 


897 


Figs   395-401. 


MOLLUSKS  :  Fig.  395,  Fasciolaria  buecinoides ;  396,  Pyrifusus  Newberryi  ;  397,  Ammo- 
nites placenta  ;  397  cr,  id.,  in  profile,  reduced  ;  39S,  Scaphites  larvaeformis  ;  39f>,  Turrilites 
catena tus  ;  400,  Baculites  ovatus  ;  401,  Belemnitella  mucronata. 


perch,  salmon,  pickerel,  etc.     They  occur  along  with  nurner- 


318 


MESOZOIC   TIME.  —  REPTILIAN   AGE. 


ous  Sharks  of  both  ancient  and  modern  types  (Cestracionts 
and  Squalodonts),  and  many  also  of  Ganoids.     Thus  the  an- 
'  cient  and  modern  forms  of  fishes  were  united  in  the  popu- 
lation of  the  Cretaceous  seas,  the  former,  however,  making 


Fig.  402. 


Osmeroides  Lewesiensis  (  x  |). 


hardly  more  than  a  tenth  of  the  species.     Fig.  402  represents 
one  of  these  Teliost  Fishes,  related  to  the  Salmon  and  Smelt, 


Figs.  403,  404. 


MOSASATJRS »  Fig,  403,  Mosasaurus  Hoffmanni  ( x  iV)  >  404,  Side  of  jaw  of  Edestosaurus 

dispar(xi). 


CRETACEOUS  PERIOD. 


319 


Fig.  405. 


tr om  the  Chalk  at  Lewes,  England.     There  were  also  Herring, 
and  many  other  kinds. 

The  Reptiles  included  species  of  several  of  the  Jurassic 
genera.  Of  these,  there  were  PTEROSAURS,  of  the  genus  Ptero- 
dactylus,  and  others,  some,  from  Kansas  rocks,  20  to  25  feet 
in  expanse  of  wing ;  ENALIOSAURS,  or  Sea-Saurians,  of  the 
genera  Ichthyosaurus,  Plesiosaurus,  etc.,  10  to  50  feet  long; 
and  DINOSAURS,  of  the  genera  Iguanodon,  Hadrosaurus,  Lcelaps 
(related  to  the  Megalosaurs),  etc.,  some  of  them  fitted  to  raise 
themselves  and  walk  on  their  hind  feet,  like  the  three-toed 
Reptiles  of  the  Triassico-Jurassic  era,  in  the  Connecticut 
Valley  (page  293). 

There  was  also  a  tribe,  unknown  before  the  Cretaceous,  that 
of  the  MOSASAURS  :  great  snake-like  Reptiles,  15  to  75  feet 
long,  swimming  by  means  of  four  paddles, 
—  literally  the  Sea-Serpents  of  the  era. 
The  remains  of  the  head  of  one,  from  the 
banks  of  the  river  Meuse  in  Holland 
(whence  the  name),  are  represented  in  Fig. 
403.  The  American  rocks  have  afforded 
forty  species  of  these  Mosasaurs.  The  head 
of  the  largest  was  four  feet  long,  and  the 
mouth  was  hence  of  enormous  size.  Be- 
sides, it  had  a  joint  in  the  lower  jaw,  either 
side,  in  place  of  the  usual  suture  (at  a,  in 
Fig.  404),  which  enabled  the  two  sides  of  a 
jaw,  as  the  bones  (rami)  wTere  not  united  at 
their  extremities,  to  act  like  a  pair  of  arms, 
iu  working  down  the  immense  throat  any 
large  animal  it  might  undertake  to  swallow 
whole.  A  tooth  of  one  of  the  Mosasaurs, 
half  the  natural  size,  is  shown  in  Fig.  405. 

Among  more  modern  kinds  of  Reptiles 

,n  .—  ,.,  ..  Tooth  of  Mosasaurus  prin 

there  were  Crocodiles  and  Turtles;  one  of          ceps(xi). 

the  latter,  from  Kansas,  15  feet  in  breadth, 

according  to  Cope,  between  the  tips  of  the  extended  flippers. 


320 


MESOZOIC   TIME.  —  REPTILIAN   AGE. 


Fig.  406-411. 


HESPERORNIS    REGALIS, 

X  &  ;  407,  lower  jaw  x  £  ;  408,' 
tooth  X  4  ;  409,  410,  vertebra} 
X  z  ;  411,  pelvis,  side  view 
X  s  '•  H,  ilium  ;  is,  ischium  ; 
1>,  pubis  ;  a,  acetabulum. 


CRETACEOUS   PERIOD. 


321 


The  Birds  in  America  included  Divers,  Cormorants,  Wad- 
ers.    Some  of  them,  as  made  known  by  Marsh,  had  teeth 


Fig. 


Ichtliyornis  victor  of  Marsh. 

like  a  Eeptile.     Fig.  406,  from  Marsh,  represents  the  skele^ 
ton   of   Hesperornis  regalis,  one-eighth   the   natural   size,  a 

23 


322 


MESOZOIC  TIME.  — REPTILIAN  AGE. 


gigantic  Diver,  5  to  6  feet  in  height,  between  an  Ostrich  and 
a  Loon  in  structure;  and  Fig.  412,  Ichthyornis  victor,  half 
the  natural  size,  a  bird  as  large  as  a  pigeon.  The  latter  had 
biconcave  vertebrae,  like  Fishes  and  Ichthyosaurs. 

3.    General  Observations. 

1.  Geography.  —  In  North  America  the  position  of  the  Cre- 
taceous beds  along  the  borders  of  the  Atlantic  south  of  New 
York,  near  the  Mexican  Gulf,  and  also  over  a  large  part  of 
the  Rocky  Mountain  region,  indicates  that  these  border  re- 
gions and  a  large  part  of  the  Western  Interior  were  under 

Tig.  413. 


North  America  in  the  Cretaceous  Period ;  MO,  Upper  Missouri  region. 

water  when  the  period  opened,  as  represented  in  the  above 
map  (Fig.  413).  The  shaded  part  of  the  continent  exhibits 
the  extent  to  which  it  was  submerged.  (This  map  should  be 


CRETACEOUS  PERIOD. 

compared  with  that  on  page  199.)  It  shows  that  the  Chesa- 
peake and  Delaware  gulfs  were  in  the  ocean ;  that  Florida 
was  still  under  water ;  that  the  region  of  the  Missouri  Eiver 
was  a  salt-water  region ;  that  the  Eocky  Mountain  region  was 
largely  submerged.  This  mountain  region  was  in  some  parts 
at  least  10,000  feet  lower  than  now,  the  Cretaceous  beds  hav- 
ing this  elevation  upon  it.  The  Mexican  Gulf  spread  over 
a  large  part  of  Georgia,  Alabama,  and  Mississippi,  extended 
northward  to  the  mouth  of  the  Ohio,  and  then,  west  of 
Missouri  and  Kansas,  stretched  far  north  over  the  present 
slopes  of  the  great  Western  mountains,  reaching  perhaps  to 
the  Arctic  Ocean,  though  on  this  point  the  evidence  is  not  yet 
decisive.  The  deposits,  excepting  those  of  Texas,  appear  to 
be  of  sea-shore  and  off-shore  formations ;  the  Texan  compact 
limestones  were  probably  formed  in  clear  interior  waters. 

In  Europe  the  Chalk  appears  to  have  been  accumulated  in 
an  open  sea,  where  the  water  was  some  hundreds  of  feet  deep. 
The  material  of  the  Chalk  has  been  stated  on  page  313  to  be 
mainly  the  shells  of  Rhizopods,  and  that  of  the  associated  flint 
to  have  been  derived  largely  from  Diatoms  and  Sponges.) 
Ehizopods,  Diatoms,  and  Sponges  are  now  living  in  man}/ 
parts  of  the  ocean,  over  the  bottom,  even  where  the  depth  is 
thousands  of  feet ;  and  the  Ehizopods  are  making  chalk-like 
accumulations  of  vast  area.  There  are,  hence,  in  the  present 
seas,  the  conditions  requisite  for  making  chalk,  and  also  flint. 
The  fossils  of  the  Chalk  are  in  many  regions  turned  into  flint, 
and  some  hollow  specimens  are  filled  with  quartz  crystals,  or 


2.  Climate.  —  The  corals  and  other  tropical  life  of  the  rock;^ 
indicate  that  the  British  seas  were  at  least  warm-temperate 
to  latitude  60°  north.  On  the  American  side  the  temper- 
ature of  the  waters  appears  to  have  been  cooler,  as  it  now 
is,  in  corresponding  latitudes ;  and  still  it  was  considerably 
warmer  than  the  present.  The  warm  oceanic  zone  which 
spread  over  the  British  seas  appears,  from  the  distribution  of 
the  fossils,  to  have  reached  the  North  American  coast  south 


324  MESOZOIC  TIME. 

of  Long  Island,  and  probably  had  no  place  on  the  coast  north 
of  Cape  Hatteras.  The  plants  of  the  Upper  Missouri  region 
indicate  a  warm-temperate  climate  over  that  territory. 

GENERAL  OBSERVATIONS  ON  THE  MESOZOIC. 

1.  Time-Ratios.  —  The  ratios  between  the  Paleozoic  ages  as 
to  the  length  of  time  that  elapsed  during  their  progress,  or 
their  time-ratios,  are  stated  on  page  269  as  probably  not  far 
from  4:1:1.     By  the  same  method,  it  follows  that  the  ratio  for 
the  time  of  the  Paleozoic  and  Mesozoic  was  nearly  4:1;  and 
for  the  Triassic,  Jurassic,  and  Cretaceous  periods,  1 : 1  j  :  1. 
That  is,  Mesozoic  time  was  about  one  fourth  as  long  as  the 
Paleozoic;  and  the  three  periods  of  the  Mesozoic  were  not 
far  from  equal,  the  Jurassic  being  one  quarter  the  longest. 

2.  America!)  Geography.  —  On  page  285  it  is  remarked  that 
the  Mesozoic  formations  were  confined  to  the  Atlantic  and 
Gulf-border  regions,  and  to  an  interior  region  west  of  the 
Mississippi  covering  much  of  the  Ptocky  Mountain  area,  and 
that  the  intervening  portion  of  the  continent  had  probably 
become  part  of  the  dry  land.     The  facts  which  have  been 
presented  in  the  preceding  pages  have  sustained  this  state- 
ment.    The  Triassico-Jurassic  beds,  as  has  been  shown,  lie  in 
long  narrow  strips  between  the  Appalachians  and  the  coast, 
and  spread  widely  over  the  Rocky  Mountain  region  and  west 
nearly  to  the  Pacific.     The  Cretaceous  beds  cover  the  Atlantic 
and  Gulf  borders,  and  also,  like  the  Triassic,  a  very  large  part 
of  the  slopes  of  the  Rocky  Mountains  and  the  Pacific  border 
west  of  the  Sierra  Nevada.     The  eastern  half  of  the  continent 
during  the  Mesozoic  was,  therefore,  receiving  rock-formations 
only  along  its  borders,  while  the  western  half  had  marine 
deposits  in  progress  over  its  great  interior  and  on  the  ocean's 
border. 

The  American  Mesozoic  deposits,  for  the  most  part,  do  not 
bear  evidence  that  they  were  formed  in  a  deep  ocean.  They 
appear  to  have  accumulated  m.unly  along  coasts,  or  in  shallow 


REPTILIAN  AGE.  325 

waters  off  coasts,  or  in  shallow  inland  seas  ;  the  Cretaceous 
limestone  of  Texas  indicates  a  pure  sea,  like  that  required  for 
coral-reefs,  but  not  necessarily  one  of  great  depth. 

The  Appalachians  —  the  eastern  mountains  of  the  continent 
—  had  nearly  their  present  elevation  before  the  early  Meso- 
zoic beds  commenced  to  form  (page  283).  But  the  region  of 
the  Rocky  Mountains  —  the  western  chain  —  was  to  a  great 
extent  still  a  shallow  sea  even  during  the  Cretaceous  period, 
or  when  the  Mesozoic  era  was  drawing  to  its  close  (page  320). 

Only  one  series  of  mountain-elevations  can  be  pointed  out, 
with  our  present  knowledge,  as  originating  in  Eastern  North 
America  in  the  course  of  the  Mesozoic  era,  although  great 
oscillations  of  level  were  much  of  the  time  in  progress.  This 
one  is  that  of  the  Mesozoic  red  sandstone  and  trap  along  the 
Atlantic  border  region,  as  explained  on  page  307. 

On  the  western  side  of  the  continent  the  mountain-making 
after  the  Jurassic  was  on  a  far  grander  scale,  the  Sierra  Ne- 
vada and  other  high  ranges  dating  from  this  epoch. 

3.  European  Geography.  —  Europe  has  its  Mesozoic  rocks 
distributed  in  patches,  or  in  several  independent  or  nearly 
independent  areas,  which  show  that  it  retained  its  condition 
of  an  archipelago  throughout  Mesozoic  time.  The  oscillations 
of  level,  as  indicated  by  the  variations  in  the  rocks,  —  varia- 
tions both  as  to  the  nature  of  the  beds  and  their  distribution, 
-  were  more  numerous  and  irregular  than  in  North  America, 
The  mountain-elevations  formed,  however,  were  few  and  small 
compared  with  those  that  followed  either  the  Paleozoic  or 
'  the  Mesozoic  era.  One  series  of  disturbances  is  referred  to 
the  close  of  the  Triassic,  and  another  to  that  of  the  Jurassic. 

Among  the  Mesozoic  formations  of  the  European  continent 
there  are  deposits  of  all  kinds,  —  those  of  sea-shores ;  of  off- 
shore shallow  waters  ;  of  inland  seas ;  of  moderately  deep 
oceanic  waters ;  and  of  marshy,  or  dry  and  forest-covered 
knd. 

Both  in  America  and  Europe  there  were  some  coal-beds 
made,  though  of  small  extent  compared  with  those  of  the 
Carboniferous  age. 


326  MESOZOIC  TIME. 

4.  Life.  —  The  Mesozoic  era  witnessed  —  (1)  the  decline  of 
some  ancient  or  Paleozoic  types  of  both  plants  and  animals, 
(2)  the  increase  and  culmination  of  mediaeval  or  Mesozoic 
types,  and  (3)  the  beginning  of  some  of  the  most  important 
of  modern  or  Cenozoic  types. 

7.  Disappearance  of  Ancient  or  Paleozoic  features.  —  Among  the 
ancient  tribes  of  plants,  the  Calamities,  or  Tree-rushes,  and 
several  genera  of  Ferns,  disappear  injbhe  Jurassic.  Among 
the  old  Brachiopod  tribes,  the  Spirifer  and  Leptcena  families 
end  in  the  Triassic ;  among  higher  Mollusks,  the  Silurian  type 
of  Ortkoceras,  and  Devonian  of  Goniatites,  have  their  last 
species  in  the  Triassic ;  in  Fishes,  the  Ganoids  lose  the  verte- 
brated  feature  of  their  tails,  characterizing  them  in  the  Paleo- 
zoic, in  the  same  period,  and  thus  bear  evidence  of  progress. 

2.  Progress  in  Mesosoic  features.  — The  Cycads,  among  plants, 
were  those  most  characteristic  of  the  Mesozoic :  they  after- 
ward yielded  to  other  kinds,  and  now  are  nearly  an  extinct 
tribe.  The  Cephalopods,  among  Mollusks,  existed  in  vast 
numbers,  both  those  with  external  shells,  as  the  Ammonites, 
and  those  without,  as  the  Belcmnites.  The  whole  number  of 
species  of  Cephalopods  now  known  from  the  Mesozoic  forma- 
tions is  nearly  1,200.  Of  these,  about  950  were  of  the  Nau- 
tilus and  Ammonite  families.  No  Ammonite  now  exists,  and 
the  only  chambered  species  which  are  now  living  are  2  or  3  of 
the  genus  Nautilus.  The  whole  number  of  species  of  Cephal- 
opods living  in  the  course  of  the  Mesozoic  era  may  have  been 
three  or  four  times  1,200,  since  only  a  part  would  have  been 
preserved  as  fossils.  The  sub-kingdom  of  Mollusks,  therefore, 
culminated  in  the  Mesozoic  era ;  for  its  highest  order,  that  of 
the  Cephalopods,  was  then  ;it  its  maximum. 

The  type  of  Eeptiles  was  another  that  expanded  and  reached 
its  height,  —  that  is,  its  maximum  in  number,  variety,  and 
rank  of  species,  —  and  commenced  its  decline  in  the 'Mesozoic 
era. 

There  were  huge  swimming  Saurians,  Enaliosaurs,  in  the 
place  of  whales  in  the  sea ;  bat-like  Saurians  or  Pterodactyls 


REPTILIAN  AGE,  327 

flying  through  the  air ;  four-footed  Saurians,  both  grazing  and 
carnivorous,  many  of  them  25  to  50  feet  long,  occupying  the 
marshes  and  estuaries;  great  biped  Saurians  or  Dinosaurs 
over  the  land ;  and  snake-like  Mosasaurs  in  the  ocean,  some 
having  the  great  length  of  75  or  80  feet. 

In  the  era  of  the  Wealden  and  Lower  Cretaceous  there  lived, 
in  and  about  Great  Britain,  4  or  5  species  of  Dinosaurs  20  to 
50  feet  long,  10  to  12  Crocodilians,  Lizards,  and  Enaliosaurs 
10  to  50  feet  long,  besides  Pterodactyls  and  Turtles;  and 
many  more  than  this,  since  all  that  lived  would  not  have  left 
their  remains  in  the  deposits.  To  appreciate  this  peculiarity 
of  mediaeval  time,  it  should  be  considered  that  in  the  present 
age  Britain  has  no  large  Eeptiles ;  in  Asia  there  are  only  two 
species  over  15  feet  in  length;  in  Africa  but  one;  in  all 
America  but  three ;  in  the  whole  world  not  more  than  six ; 
and  the  largest  of  the  six  does  not  exceed  25  feet  in  length. 
North  America,  during  the  Cretaceous,  appears  to  have  ex- 
ceeded all  the  world  beside  in  the  number  and  size  of  its  Eep- 
tiles. The  Mesozoic  era  is  well  named  the  Age  of  Eeptiles. 

All  the  Mesozoic  animals,  excepting  the  Mammals,  belong 
to  the  oviparous  divisions ;  and  the  Mammals  were  mainly 
Marsupial  species,  —  that  is,  semi-oviparous  Mammals,  as  ex- 
plained on  page  176,  —  species  quite  in  harmony,  therefore, 
with  the  other  life  of  the  era.  The  Birds  of  the  age,  or  at 
least  some  of  them,  partook  of  the  Eeptilian  features  of  the 
time,  having  long  tails  like  the  associated  Eeptiles  (though 
feathered  tails),  with  other  peculiarities  of  the  scaly  tribes ; 
and  some  even  had  reptile-like  teeth.  The  long-tailed  birds 
and  Pterodactyls  were  the  flying  creatures  of  the  age ;  the 
Ichthyosaurs  and  Plesiosaurs,  and  the  like,  the  "  great  whales  "  ; 
the  Teleosaurs,  Iguanodon,  and  other  gigantic  species  of  the 
estuaries  and  marshes,  the  creeping  species.  These,  along 
with  the  small  Marsupials  of  the  Cycadean  and  Coniferous 
forests,  were  the  more  prominent  kinds  of  Mesozoic  life. 

3.  Introduction  of  Cenozoic  features.  —  Among  plants  the 
first  of  Angiosperms  (or  the  order  including  all  trees  having 


328  MESOZOIC  TIME. 

a  bark  excepting  the  Conifers,  as  the  Oak,  Maple,  Apple,  etc.), 
and  the  first  of  Palms  are  found  in  the  Cretaceous.  These 
become  the  characteristic  plants  of  Cenozoic  time. 

Among  Vertebrates  there  was  a  great  expansion,  if  not  the 
first,  of  the  great  order  of  Teliost  or  Osseous  Fishes,  the  species 
characteristic  of  earlier  time  having  been  either  Selachians 
(Shark  tribe),  Ganoids,  or  Placoderms  (page  237).  The  first 
of  the  modern  genus  of  Crocodilus  occurs  in  the  Jurassic ;  the 
first  of  Birds  in  the  Triassic  or  Jurassic,  —  the  Reptilian 
Birds  ;  the  first  of  Mammals  in  the  Triassic,  —  Marsupials,  or 
semi-oviparous  Mammals. 

Of  the  classes  of  Vertebrates^Fishes  and  Reptiles  commence 
in  the  middle  and  later  Paleozoic,  and  Birds  and  Mammals 
in  the  early  or  middle  Mesozoic. 

Extermination  of  life  at  the  close  of  the  Cretaceous.  —  At  the 
.  close  of  the  last  period  of  the  Mesozoic  era  —  the  Cretaceous 
—  there  was  an  extermination  of  species  over  a  large  part  of 
the  Continental  seas  as  complete  as  that  closing  the  Paleozoic 
era.  In  Europe,  Asia,  and  Eastern  North  America  no  Cre- 
taceous species  have  been  found  fossil  in  any  Tertiary  strata. 
In  the  Rocky  Mountain  region  and  the  Pacific  border  it  is 
probable  that  some  Cretaceous  species  continued  on  into  the 
Tertiary,  as  stated  beyond  (page  337).  There  is  no  reason  for 
asserting  that  the  species  of  the  open  ocean  were  exterminated ; 
on  the  contrary,  it  is  believed  that  at  least  one  Cretaceous 
Mollusk" —  a  Terebratula  —  still  exists  in  the  depths  of  the 
Atlantic. 

Besides  the  destruction  of  species,  there  was  the  final  ex- 
tinction of  several  families  and  tribes.  The  great  family  of 
Ammonites,  and  many  others  of  Mollusks,  all  the  genera  of 
Reptiles  excepting  Crocodilus,  and  others  in  all  departments 
of  life,  came  to  their  end  at  the  close  of  the  Cretaceous  or 
soon  after. 

Extermination  over  so  wide  a  range  of  Continental  seas 
must  have  been  due  to  a  cause  which  acted  as  widely,  and 
no  other  appears  to  be  sufficient  excepting  a  change  of  climate 


CENOZOIC  TIME.  329 


in  the  north.  The  Arctic  and  other  high-latitude  regions 
may  have  been  elevated  more  than  those  of  lower  latitudes, 
for  Tertiary  rocks  do  not  occur  on  the  eastern  borders  of  the 
American  continent  north  of  the  parallel  of  42°  1ST.  to  show 
that  the  continent  was  then  below  its  present  level.  Con- 
nected with  the  elevation  of  the  land  to  the  north  there  may 
have  been  an  exclusion  of  warm  oceanic  currents  from  the 
Arctic  seas ;  for  in  Behring  Straits  the  depth  of  water  is  less 
than  200  feet.  By  these  means  a  semi-glacial  epoch  may  have 
been  occasioned  which  sent  cold  oceanic  currents  from  the 
north  along  the  sea-borders  and  Continental  seas  to  the  south. 
Should  the  cold  winds  and  cold  oceanic  currents  of  the  north- 
ern part  of  the  existing  temperate  zone  penetrate  for  a  single 
year  into  the  tropical  regions,  they  would  produce  a  general 
extermination  of  the  plants  and  animals  of  the  land,  and  also 
of  those  of  the  coast  and  sea-borders,  as  far  as  the  cold  oceanic 
currents  extended.  A  change  to  a  climate  no  colder  than  the 
present  would  have  been  sufficient  probably  for  all  the  de- 
struction that  took  place,  since  the  life  of  the  Cretaceous  seas, 
even  in  Northern  Europe,  was  largely  that  of  the  warm-tem- 
perate zone. 

While  the  emergence  of  northern  lands  here  appealed  to 
may  have  taken  place  as  the  Cretaceous  period  closed,  there 
appears  to  have  been  no  mountain-making  of  much  extent 
until  the  Tertiary  age  had  already  far  advanced  (page  346). 


IV. -CENOZOIC    TIME. 

1.  CENOZOIC  TIME  covers  two  ages :  1.  THE  TERTIARY  AGE, 
or  AGE  OF  MAMMALS  ;  and  2.  THE  QUATERNARY,  or  AGE  OF 
MAN. 

2.  General  characteristics. — In  the  transition  to  this  era  the 
life  of  the  world  takes  on  a  Dew  aspect.     Trees  of  modern 
types  —  Oak,  Maple,  Beech,  etc.,  and  Palms  —  unite  with 


330  CENOZOIC  TIME. 

Conifers  to  make  the  forests;  Mammals  of  great  variety  and 
size,  —  Herbivores,  Carnivores,  and  others,  successors  to  the 
small  semi-oviparous  Mammals,  tenant  the  land  in  place  of 
Reptiles ;  Birds  and  Bats  possess  the  air  in  place  of  reptilian 
Birds  and  Pterodactyls ;  Whales  and  Teliost  or  common 
Fishes,  with  Sharks,  mainly  of  modern  type,  occupy  the 
waters  in  place  of  Enaliosaurs,  and  almost  to  the  exclusion 
of  the  ancient  tribes  of  Cestraciont  Sharks  and  Ganoids. 
Finally  Man  appears  when  Mammals  were  passing  their 
maximum  in  grade  and  magnitude,  and  becomes  the  domi- 
nant species  of  the  finished  world. 

'I.   TERTIARY  AGE,   or   AGE   OP   MAMMALS. 

The  Mammals  of  this  age  are  all  extinct  species,  and  the 
other  species  of  life  largely  so ;  the  number  of  living  species 
of  Invertebrates  (Radiates,  Mollusks,  and  Articulates)  varies 
from  perhaps  one  per  cent  in  the  early  part  of  the  age  to 
90  in  the  latter.  In  the  Quaternary  the  Mammals  of  the 
earlier  part  are  nearly  all  of  extinct  species  ;  the  Invertebrates 
are  almost  wholly  of  living  species. 
I .  Periods. 

The  Tertiary  strata  have  been  divided  by  Lyell  into  three 
groups : 

1.  Eocene  (from  the  Greek  ydx;,  dawn,  and  KCLLVQS,  recent) : 
species  nearly  all  extinct. 

2.  Miocene  (from  nelcov,  less,  and  /catuo?)  :  less  than  half 
the  species  living. 

3.  Pliocene  (from  TrXetW,  more,  and  /caivos) :   more  than 
half  the  species  living. 

These  subdivisions  are  not  necessarily  those  marked  off 
by  the  grander  physical  changes  of  a  continent. 

In  North  America  there  was :  — 

1,  The  Lignitic  period,  corresponding  to  the  Lower  Eocene, 
or  else   intermediate   between   the  Tertiary  and  Cretaceous. 


TERTIARY  AGE.  331 

The  beds  follow  on  conformably  after  the  Cretaceous;  and 
then,  as  the  period  closed,  these  Lignitic  strata,  along  with 
the  underlying  Cretaceous,  which  were  also  largely  lignitic, 
were  together  upturned,  lifted  into  mountains,  and  partly  ren- 
dered metamorphic ;  and  this  happened  both  in  the  Eocky 
Mountain  region  and  in  California.  This  mountain-making 
epoch  makes  a  natural  ending  of  the  period. 

2.  The  Alabama   period,  corresponding   to   the   remainder 
of  the  Eocene.      The  beds  in  the  Rocky  Mountain  region 
overlie  nearly  or   quite   horizontally  the  upturned  Lignitic 
and  Cretaceous  beds.     On  the  Gulf  of  Mexico  they  include 
the  marine  beds  of  Claiborne,  Alabama,  and  of  Jackson  and 
Vicksburg,  Mississippi.     The  close  of  the  period  was  marked 
off  by  a  change  over  the  lower  part  of  the  Mississippi  Valley 
about  the  Gulf;   for   no  marine  Tertiary  strata  later  than 
Eocene  exist  in  those  regions.     The  country  in  the  line  of 
Florida  to  the  northwest,  now  300  to  700  feet  above  the  sea- 
level,  is  the  western  boundary  of  the  area  of  the  later  Ter- 
tiary. 

3.  Yorktown,  or  that  of  the  beds  of  Yorktown,  Virginia,  in 
which  20  to  40  per  cent  of  the  species  are  living,  —  usually 
called  Miocene,  but  possibly  including  part,  at  least,  of  the 
Pliocene. 

A  fourth  has  been  separated  as  Pliocene,  or  the  Sumter 
epoch,  based  on  observations  on  the  beds  in  Sumter  and  Dar- 
lington districts,  South  Carolina ;  but  according  to  Conrad,  it 
may  not  be  distinct  from  the  Yorktown. 

2.    Rocks:   Kinds  and  Distribution. 

The  beds  are  either  of  marine  or  of  fresh-water  origin. 

The  marine  Tertiary  beds  of  North  America  border  the 
continent  south  of  New  England  along  both  the  Atlantic 
Ocean  and  the  Mexican  Gulf,  overlying  the  Cretaceous  in 
part.  The  most  northern  locality  is  on  Martha's  Vineyard. 
(See  map,  page  195,  in  which  the  area  is  lined  obliquely  from 
the  left  above  to  the  right  below.)  They  spread  northward 


332  CENOZOIC   TIME. 

to  the  mouth  of  the  Ohio,  and  also  westward  into  Texas,  west 
of  the  Mexican  Gulf. 

The  marine  Tertiary  beds  do  not,  like  the  Cretaceous, 
stretch  north  and  northwest  up  the  eastern  slopes  of  the 
Kocky  Mountains ;  but,  instead,  there  are  over  these  slopes 
extensive  fresh-water  Tertiary  strata  (formed  in  and  about 
great  lakes),  with  in  many  places  some  of  the  lowest  beds  of 
brackish-water  origin,  as  shown  by  the  fossils.  This  fresh- 
water Tertiary  extends  over  the  summit  region  of  the  Kocky 
Mountains ;  and  there  the  lower  part  includes  not  only 
brackish-water,  but  also  salt-water,  beds,  along  with  those 
of  fresh-water  formation.  Marine  Tertiary  occurs  also  in 
California  and  Oregon,  not  far  from  the  coast. 

The  Lignitic  period,  or  early  Eocene,  includes  brackish- 
water,  and  associated  fresh-water,  strata  in  the  Upper  Mis- 
souri and  Eocky  Mountain  regions.  They  are  remarkable  for 
containing  extensive  beds  of  good  mineral  coal,  called  brown 
coal  or  lignite,  whence  the  name  of  the  period.  These  coal- 
beds  are  worked  at  Evanston,  Coalville,  and  other  places  on 
or  near  the  Central  Pacific  Eailroad.  In  Colorado  and  New 
Mexico  the  Lignitic  Tertiary  passes  downward,  according  to 
the  statements  of  some  observers,  into  lignitic  strata  that 
belong  to  the  Upper  Cretaceous. 

Lignitic  beds  underlying  the  marine  Tertiary  of  the  Missis- 
sippi Valley  south  of  the  Ohio  are  also  of  this  era. 

The  Alabama  period,  or  the  Middle  and  Later  Eocene, 
comprises  the  marine  Tertiary  of  the  Gulf  border  from  Mis- 
sissippi eastward,  and  the  lower  beds  of  the  Tertiary  forma- 
tion along  the  Atlantic  border. 

To  the  Yorktown  period,  or  Miocene,  belong  the  marine  Ter- 
tiary beds  of  the  Atlantic  border  from  New  Jersey  to  South 
Carolina,  overlying  the  Eocene  ;  and  fresh-water  strata  of  great 
extent  in  the  Upper  Missouri  region  and  elsewhere  over  the 
eastern  slopes  of  the  Eocky  Mountains. 

The  Pliocene  Tertiary,  besides  including  possibly  marine 
beds  in  South  Carolina,  as  mentioned  above,  comprises  fresh- 


TERTIARY  AGE.  333 

water  beds  in  the  Upper  Missouri  region,  and  to  the  south, 
where  they  overlie  the  Miocene  fresh-water  strata,  and,  like 
them,  are  of  lacustrine  origin. 

The  Tertiary  rocks  are  generally  but  little  consolidated ; 
they  consist  mostly  of  compacted  sand,  pebbles,  clay,  earth 
that  was  once  the  mud  of  the  sea-bottom  or  of  estuaries, 
mixed  often  with  shells,  or  are  such  kinds  of  deposits  as  now 
form  along  sea-shores  and  in  shallow  bays  and  estuaries,  or 
in  shallow  waters  off'  a  coast.  There  are  also  limestones 
made  of  shells,  and  others  of  corals,  resembling  the  reef- 
rock  of  coral  seas.  The  latter  are  found  mainly  in  the  States 
bordering  on  the  Mexican  Gulf.  Another  variety  of  rock  is 
buhrstone,  a  cellular  siliceous  rock,  flinty  in  texture,  used,  on 
account  of  its  being  so  hard  and  at  the  same  time  full  of 
irregular  cavities,  for  making  millstones.  It  is  found  iu 
South  Carolina  and  Alabama. 

The  Tertiary  of  Great  Britain  occurs  mostly  in  the  south' 
eastern  part  of  England,  in  the  London  basin  as  it  is  called, 
and  on  the  southern  and  eastern  borders  of  the  island,  adjoin- 
ing the  Cretaceous. 

On  the  continent  of  Europe  the  Paris  basin  is  noted  for  its 
Eocene  strata  and  fossil  Mammals.  Other  Tertiary  areas  are 
those  of  the  Pyrenean  and  Mediterranean  regions,  those  of 
Switzerland,  of  Austria,  etc.  Some  of  the  marine  Fig  <Li4. 
Eocene  beds  contain  Ehizopods  (p.  185)  having 
the  shape  of  a  coin,  called  Nummulite  (from 
the  Latin  nummus,  a  coin).  One  is  here  figured, 
of  natural  size  ;  it  has  the  exterior  of  half  oT 
it  removed  to  show  the  cells  within.  Occasion- 
ally  the  beds  are  so  far  made  up  of  these  Nummulites  that 
the  rock  is  called  Nummulitic  limestone. 

These  marine  Eocene  strata  spread  very  widely  over  Lu- 
rope,  Northern  Africa,  and  Asia,  —  occurring  in  the  Pyre- 
nees, forming  some  of  their  summits ;  in  the  Alps  to  a  height 
of  10,000  feet ;  in  the  Carpathians,  in  Algeria,  in  Egypt,  Avhere 
the  most  noted  pyramids  aro  made  of  Nummulitic  limestone, 


334  CENOZOIC   TIME. 

in  Persia,  in  the  Western  Himalayas  (the  region  of  Cash- 
mere), to  a  height  of  16,500  feet.  The  later  Tertiary  forma- 
tions are  much  more  limited  in  distribution,  and  many  are  of 
terrestrial  or  fresh-water  origin. 

The  rocks  are  similar  to  those  of  North  America,  but  in- 
clude more  of  hard  sandstone  and  limestone.  The  sandstone 
is  a  very  common  building-stone  in  different  parts  of  Europe, 
being  soft  enough  to  be  worked  with  facility,  yet  generally 
hardening  on  exposure,  owing  to  the  fact  that  it  contains  cal- 
careous particles  (triturated  shells),  which  render  the  perco- 
lating waters  or  rain  calcareous,  so  that  on  evaporating  they 
produce  a  calcareous  deposit,  as  a  cement,  among  the  grains 
of  sand. 

The  Eocene  formation  of  Southeastern  England  consists  of 
beds  of  clay  and  sand,  the  lowest  of  sand  sometimes  contain- 
ing rolled  flints.  The  Lower  Eocene  includes  the  Thanet 
sands,  Woolwich  beds,  and  London  clay ;  the  Middle  Eocene, 
the  lower  Bagshot  beds ;  the  Upper  Eocene,  the  Barton  clay, 
Bembridge  beds,  and  the  Hernpstead  beds  near  Yarmouth. 
The  Older  Pliocene  includes  the  Coralline  crag  and  Eed  crag 
of  Suffolk ;  and  the  Newer  Pliocene,  the  Norwich  crag,  which 
is  of  fluvio-marine  origin.  No  marine  Miocene  beds  have 
yet  been  identified  in  Great  Britain. 

I.    Life. 
1.    Plants. 

\  The  great  feature  of  the  Tertiary  vegetation  is  the  preva- 
lence of  Angiosperms,  the  tribe  of  plants  which,  thus  far,  is 
unknown  before  the  Cretaceous.  Leave?  of  Oak,  Poplar,  Maple, 
Hickory,  Dogwood,  Mulberry,  Magnolia,  Cinnamon,  Fig,  Syca- 
more, Willow,  and  many  others,  have  already  been  found  in 
both  American  and  European  Tertiary  strata,  besides  the  re- 
mains of  Palms  and  Conifers.  A  leaf  of  a  Tertiary  Fan-palm 
(species  of  Salal),  found  in  the  Upper  Missouri,  must  have 
been,  when  entire,  12  feet  in  breadth.  Nuts  are  also  common 
in  some  beds,  —  as  at  Brandon,  Vermont.  Fig.  415  is  the 


TERTIARY  AGE. 


335 


leaf  of  an  Oak  ;  Fig.  416,  of  a  species  of  Cinnamon  ;  Fig.  417, 
of  a  Palm ;  Fig.  418,  the  nut  of  a  beech,  closely  like  that  of 


Figs.  415-419. 


f'ig.  415,  Quercus  myrtifolia?;  416,  Cinnainomum  Mississippiense  ;  417,  Calamopsis  Danae ; 
418,Fagus  ferruginea?;  419,  Carpolithes  irregnlaris. 

the  common  beech ;  Fig.  419,  another  nut,  from  Brandon,  of 
unknown  relations.  Figs.  420-425. 

The  Eocene  Plants  of  Great  420 
Britain  included  Palms,  and 
among  those  of  Central  and  South- 
era  Europe  there  were  many  spe- 
cies related  to  the  trees  of  Austra- 
lia; while  the  Miocene  and  Plio- 
cene had  much  similarity  to  those 
of  America. 

The   microscopic   plants  which 
form  siliceous  shells,  called  Diatoms  (Figs.  420  to  425,  all 


Diatoms. 


336 


CENOZOIC  TIME. 


greatly  enlarged),  make  extensive  deposits  in  some  places. 
One  stratum  near  Richmond,  Virginia,  is  30  feet  thick,  and 
is  many  miles  in  extent ;  another,  near  Monterey,  California,  is 
50  feet  thick,  and  the  material  is  as  white  and  fine  as  chalk, 
which  it  resembles;  another,  near  Bilin  in  Bohemia,  is  14 
feet  thick.  The  material  from  the  latter  place  was  used  as  a 
polishing-powder  (and  called  Tripoli,  or  polishing-slate)  long 
before  it  was  known  that  its  fine  grit  was  owing  to  the  re- 
mains of  microscopic  life.  Ehrenberg  has  calculated  that  a 
cubic  inch  of  the  fine  earthy  slate  contains  about  forty-one 
thousand  millions  of  organisms.  Such  accumulations  of  Dia- 
toms are  made  both  in  fresh  waters  and  salt,  and  those  of  the 
ocean  at  all  depths. 

2.  Animals. 

The  most  prominent  fact  with  regard  to  the  Tertiary  In- 
vertebrates is  their  general  resemblance  to  modern  species. 
Although  a  number  of  the  genera  are  extinct,  and  nearly 
every  Eocene  species,  there  is  still  a  modern  look  in  the  re- 
Figs.  426-430. 


LAMELLIBRANCHS  :  Fig.  426,  Ostrea  sellseformis ;  427,  Crassatella  alta ;   428,  Astarte 
Conradi ;  429,  Cardita  planicosta.  —  GASTEROPOD  :  430,  Turritella  carinata. 

mains,  and  the  specimens  have  often  the  freshness  of  a  shell 
from  a  modern  beach. 


TERTIARY  AGE. 


337 


The  preceding  are  figures  of  a  few  Mollusks  of  the  marine 
Eocene,  from  Claiborne,  Alabama.  Fig.  426  represents  an 
Eocene  Oxtrea ;  Fig.  427,  a  species  of  Crassatella ;  Fig.  428,  an 
Astarte;  Fig.  429,  a  Cardita  ;  and  Fig.  430,  a  Turritella. 

Figs.  431  to  434  are  species  of  Miocene  shells,  from 
Virginia ;  Figs.  431, 432,  represent  a  very  common  Crepidula. 

Figs.  431-434. 
433 


GASTEROPOD  :  Figs.  431,  432,  Crepidula  costata.  —  LAMELLIBRANCHS  :  Fig.  433, 
Yoldia  liniatula ;  434,  Callista  Sayana. 

upper  and  under  sides.  The  species  of  the  epoch  include  the 
common  Oyster  and  Clam,  and  other  modern  species;  and 
these  are,  therefore,  among  the  most  ancient  of  living  species 
on  the  globe.  The  Lignitic  beds  of  the  Ilocky  Mountain 
region  in  Wyoming  Territory  and  elsewhere  contain  a  very 
few  Cretaceous  species,  among  them  the  Inoceramus  proble- 
maticus. 

"With  regard  to  Vertebrates  the  points  of  special  interest 
are  the  following  :  — 

1.  In  the  class  of  Fishes :  (1)  The  prevalence  of  Tdiosts, 
or  fishes  allied  to  the  Perch  and  Salmon,  as  already  stated ; 
and  (2)  the  abundance  of  Sharks,  some  of  them  having  teeth 
6  inches  long  and  broad.  The  teeth  of  sharks  are  the  durable 
part  of  the  skeleton ;  they  are  very  abundant  in  both  Eocene 
and  Miocene  beds.  Fig.  436  represents  a  tooth  of  the  Car- 
charodon  angustidens.  The  larger  teeth  above  alluded  to  belong 
to  the  Oarcharodon  megalodon,  and  are  found  at  different  places 
on  the  Atlantic  border  from  Martha's  Vineyard  southward. 

22 


338 


CENOZOIC  TIME. 


Figs.  435,  436 


Fig.  435  represents  the  tooth  of  another  common  kind  t>f 
Shark,  a  species  of  Lamna,  from  Claiborne. 

In  the  class  of  Reptiles :  The  existence  of  numerous  Croco- 
diles and  Turtles.     The  shell  of  one  of  the  Miocene  turtles, 

found  fossil  in  India,  had  a  length  of 
12  feet,  and  the  animal  is  supposed 
to  have  been  20  feet  long.  The  first 
of  true  Snakes,  moreover,  occur  in 
the  Eocene. 

Dinosaurian  remains,  unknown  in 
Europe  above  the  Cretaceous,  occur 
sparingly  in  the  Lignitic  beds  of  the 
Rocky  Mountain  region,  and  have 
strengthened  the  doubt  whether  these 
beds  are  not  part  of  the  Upper  Cre- 
taceous. 

In  the  class  of  Birds  :  The  species 
found  are  not  long-tailed,  or  in  any 
respect  reptilian,  but  resemble  mod- 
ern birds  ;  they  are  related  to  the 
Pelican,  Waders,  Pheasants,  Perclicrs, 
TEETH  OF  SHARKS.  -  K,  486,  ™twre,,  Owls,  Woodpeckers,  and 

Carcharodon    angustidens ;    435,    Other  Kinds. 
Lamna  elegans.  T        f-i 


The 

occurrence  of  the  first  of  Whales,  the  first  of  Carnivores,  Her- 
bivores, Rodents,  Monkeys,  and  of  other  tribes,  indicating  a 
large  population  of  brute  animals,  different  from  the  present 
in  species,  though,  in  general,  related  to  the  modern  kinds 
in  form  and  structure.  A  few,  however,  are  widely  diverse 
from  anything  in  existence,  —  such  combinations  as  the  mind 
would  never  have  imagined  without  aid  from  the  skeletons 
furnished  by  the  strata. 

In  the  early  Eocene  there  appear  to  have  been  more  Her- 
bivores than  Carnivores ;  but  afterward  the  Carnivores  were 
as  common  as  now. 

Cuvier  first  made  known  to  science  the  existence  of  fossil 


TERTIARY  AGE. 


339 


Tertiary  Mammals.  The  remains  from  the  earthy  beds  about 
Paris  had  'been  long  known,  and  were  thought  to  be  those  of 
modern  beasts.  But,  through  careful  study  and  comparisons 
with  living  animals,  he  was  enabled  to  bring  the  scattered 
bones  together  into  skeletons,  ascertain  the  tribe  to  which 
they  belonged,  and  determine  the  food  and  mode  of  life  of  the 
ancient  but  now  extinct  species.  Cuvier  acquired  his  skill 
by  observing  the  mutual  dependence  which  subsists  between 
all  parts  of  a  skeleton,  and,  in  fact,  all  parts  of  an  animal.  A 
sharp  claw  is  evidence  that  the  animal  has  trenchant  or  cut- 
ting molar  teeth,  and  is  a  flesh-eater ;  a  hoof,  that  he  has  broad 
molars  and  is  a  grazing  species ;  and,  further,  every  bone  has 
some  modification  showing  the  group  of  species  to  wrhich  it 
belongs,  and  may  thus  be  an  indication,  in  the  hands  of  one 
well  versed  in  the  subject,  of  the  special  type  of  the  animal, 
and  of  its  structure,  even  to  its  stomach  within  and  its  hide 
without. 

One  of  these  Paris  beasts  from  the  middle  Eocene  beds  is 
called  a  Palcotherc,   from  the  Greek  vraXato?,   ancient,   and 
v,  wild  beast.     It  is  related  to  the  modern  Tapirs  (Fig. 

Fig.  437- 


Tapirus  Indicus. 


437),  and  was  of  the  size  of  a  horse.     Another  kind,  called  a 
Xiphodon,  was  of  more  slender  habit,  and  somewhat  resembled 


340  CENOZOIC  TIME. 

a  stag,  as  shown  in  Fig.  438.  There  were  others,  related  to  the 
hog,  or  Mexican  Peccary ;  also  some  Carnivores,  a  Bat,  and  an 
Opossum. 

Among  American  Eocene  Mammals  there  is  a  species  of 
whale  of  great  length,  called  a  Zeuglodon,  from  %6vy\Tj,  yoke, 
and  o5ou9,  tooth,  in  allusion  to  the  fact  that  part  of  the  teeth 
have  two  long  prongs  which  give  them  a  yoke-like  shape. 

Fig   438 


Xiphodon  gracile. 

The  bones  occur  in  many  places  in  the  Gulf  States,  and  in 
Alabama  the  vertebrae  were  formerly  so  abundant  as  to  have 
been  built  up  into  stone  walls,  or  burned  to  rid  the  fields  of 
them.  The  living  animal  was  probably  70  feet  in  length. 
One  of  the  larger  vertebrae  measures  a  foot  and  a  half  in  length 
and  a  foot  in  diameter. 

The  Lignitic  beds,  or  early  Eocene  of  North  America,  have 
afforded  no  Mammalian  remains.  But,  from  the  overlying 
Middle  or  Later  Eocene,  of  the  Green  Eiver  basin,  near  Fort 
Bridger,  a  large  number  of  species  have  been  obtained.  The 
skull  of  one  kind,  of  elephantine  size,  having  six  horn-cores, 
and  called  by  Marsh  Dinoceras,  in  allusion  to  its  horns,  is  rep- 
resented in  Fig.  341.  It  was  somewhat  related  to  the  Ehino- 
ceros.  There  were  also  the  earliest  of  the  Horse  tribe,  called 
Orohippus ;  and  it  is  remarkable  that  these  Eocene  Horses 
had  four  usable  toes  (Fig.  440)  instead  of  the  one  only  of  the 


TERTIARY   AGE. 


341 


modern  Horse.     The  relations  in  the  foot  of  the  latter  to  dif- 
ferent kinds  of  Tertiary  Horses  are  illustrated  in  Figs.  440  -  443. 

Fig.  439. 


Dinoceras  mirabile  (  x  |). 

In  Fig.  443  it  is  shown  that  the  modern  Horse  has  one 
usable  toe,  the  third,  and  rudiments  of  two  others,  the  second 


Figs.  440-443 
441 


443 


\ 


EZ 

FEET  OF  SPECIES  OF  THE  HORSE  TRIBE. -Fig.  440,  Orohippus,  of  "the  Eocene 
(x  |-);  441,  Anchitherium,  of  the  Miocene;  442,  Hipparion.  of  the  Pliocene ;  443,  the 
modern  Horse. 


342 


CENOZOIC  TIME. 


and  fourth,  in  what  are  called  the  splint-bones.  In  the  Hip- 
parion,  of  the  Pliocene  (Fig.  442),  the  second  and  fourth  have 
hoofs,  but  they  are  not  usable.  In  Anchitherium,  of  the  Mio- 
cene (Fig.  441),  the  second  and  fourth  toes  come  to  the  ground, 
and  are  therefore  usable.  In  Orohippus  (Fig.  440),  not  larger 
than  a  small-sized  dog,  there  are  four  toes,  and  all  are  usable. 

Other  "Wyoming  species  are  related  to  the  Tapir  and  Hog, 
some  approaching  in  characters  the  Paris  Paleotliere.  There 
were  also  Monkeys,  some  Carnivores  related  to  the  Cat  and 
Wolf,  Bats,  Squirrels,  Moles,  and  Marsupials. 

The  Miocene  beds  of  the  "  Bad  Lands  "  on  the  White  Kiver, 
in  the  Upper  Missouri  region  and  elsewhere  in  the  West,  have 
afforded  remains  of  other  Mammals. 


Among  them  are  several 


Fig.  444. 


Tooth  of  Titanotherium  Proutii  (X  4)- 

Carnivores  related  somewhat  to  the  Hyena,  Dog,  and  Panther  ; 
many  Herbivores,  including  Rhinoceroses,  species  approaching 
the  Tapir,  Peccary,  Deer,  Camel,  Horse;  Kodents.  Fig.  444 

Fig.  445. 


Teeth  of  Rhinoceros  (Hyracodon)  Nebrascensis. 

represents  a  tooth,  half  the  natural  size,  of  a  Titanothere,  an 
animal  related  to  the  Tapir  and  Paleothere,  but  of  elephan- 
tine size,  standing  probably  7  or  3  feet  high.  Fig.  445  repre- 


TERTIARY  AGE. 


343 


sents  a  few  of  the  teeth  of  an  animal  related  to  the  Khinoceroses. 
Another  species,  the  Brontotherium,  nearly  as  large  as  an 
Elephant,  but  related  somewhat  to  the  Rhinoceros,  had  a  pair 
of  great  horns. 


Fig    440. 


Oreodun  gracilis. 


Fig.  446  represents  the  skull  of  another  Miocene  Mammal, 
called  an  Oreodon,  which  is  intermediate  between  the  Deer, 


Camel,   and  Hog.      Remains    of 


Fig   447. 


Camel  and  Rhinoceros,  and  some  of 
the  tapir-like  beasts,  have  been 
found  in  the  Miocene  of  the  Atlan- 
tic border. 

In  the  Pliocene  beds  of  the 
Upper  Missouri  region  still  other 
species  occur;  including  Camels,  a 
Rhinoceros,  an  Elephant,  a  Masto- 
don, Horses,  Deers,  a  Wolf,  a  Fox, 
a  Tiger,  —  a  range  of  species  quite 
Oriental  in  character. 

Among  Mammals  of  the  Euro- 
pean Miocene  there  were  Elephants,  Mastodons,  Deer,  and 


Dinotherium  giganteum  (x  4TT). 


344 


CENOZOIC   TIME. 


other  Herbivores,  many  Carnivores,  Monkeys,  Ant-eaters,  etc. 
One  of  the  most  singular  species  is  the  Dinothere,  the  form 
of  the  skull  of  which  is  shown  in  Fig.  447 ;  its  actual  length 
is  3  feet  8  inches.  It  appears  to  have  had  a  proboscis  like 
an  Elephant,  but  the  tusks  proceeded  from  the  lower  instead 
of  upper  jaw,  and  were  bent  downward. 

The  earliest  of  the  Bovine  or  Ox  group  occur  in  the  Euro- 
pean Pliocene. 

4.  General  Observations. 

1.  Geography.  —  The  Tertiary  period  completed  mainly  the 
work  of  rock-making  along  the  borders  of  the  continent,  which 

Figs   448 


Map  of  North  America  in  the  early  part  of  the  Tertiary  Period. 

had  been  in  progress  during  the  Cretaceous  period.  The  ac- 
companying map  shows  approximately  the  part  of  the  conti- 
nent of  North  America  under  the  sea  toward  the  middle  of 


TERTIARY  AGE.  345 

the  Eocene  Tertiary,  or  when  the  Lignitic  period  was  near  its 
close.  By  comparing  it  with  the  map  of  the  Cretaceous  con- 
tinent, page  322,  it  is  seen  that  in  the  interval  the  Kocky 
Mountain  region  had  become  dry  land.  The  occurrence  of 
brackish- water  beds  in  the  Lignitic  Tertiary  of  the  Upper 
Missouri  region,  and  of  salt-water  beds,  as  well  as  brackish- 
water,  in  the  Lignitic  of  the  summit  of  the  mountains,  indicate, 
as  shown  by  Hayden,  that  the  passage  from  the  marine  condi- 
tion of  the  Cretaceous  era  gradually  changed  into  that  of  the 
fresh-water  lakes  and  dry  land  of  the  later  Eocene.  The 
gradualuess  of  the  transition  is  further  shown  in  the  occur- 
rence of  Lignitic  or  coal-bearing  beds  in  the  Upper  Creta- 
ceous. After  the  Eocene,  the  elevation  went  forward,  but 
still  with  extreme  slowness,  for  in  the  Miocene  the  eastern 
slopes  of  the  mountains  were  covered  with  immense  fresh- 
water lakes,  whose  borders  were  the  haunts  of  the  Mammals 
of  the  era ;  and  these  lakes  were  continued,  though  of  dimin- 
ished size,  into  the  Pliocene.  The  Cretaceous  beds  are  now 
10,000  feet  above  the  sea-level,  showing  that  this  amount  of 
elevation  has  taken  place  since  that  era ;  but  this  height  may 
not  have  been  fully  attained  before  the  closing  part  of  the 
Pliocene  period.  The  area  of  the  Mississippi  river-system, 
embracing  the  slopes  of  the  Eocky  Mountains  on  the  west 
and  those  of  the  Appalachians  on  the  east,  then  for  the  first 
time  attained  its  full  dimensions.  The  Mexican  Gulf  was 
much  larger  in  the  Eocene  period  than  at  present ;  but  there 
was  not  that  long  extension  northward  which  it  had  during 
the  Cretaceous  period.  Florida  was  still  submerged,  and  also 
all  the  bays  of  the  Atlantic  coast  south  of  New  York.  After 
the  Eocene  epoch  the  Mexican  Gulf  became  much  more  con- 
tracted by  an  elevation  of  the  coast  along  the  Gulf,  accom- 
panying which  the  part  of  Georgia  northwest  of  Florida, 
where  Eocene  and  Cretaceous  beds  had  been  formed  in  the 
sea,  was  raised  300  to  700  feet  above  the  sea-level.  By  the 
close  of  the  Tertiary  period  the  continent  appears  to  have 
reached  nearly  its  present  outline. 


346  CENOZOIC  TIME. 

Besides  the  gradual  changes,  there  was  in  the  Eocky  Moun- 
tain region,  and  also  in  California,  the  making  of  mountain 
ranges.  At  the  close  of  the  Lignitic  period  there  were  up- 
turnings  of  the  Lignitic  and  underlying  formations  ;  and  the 
Wahsatch,  with  other  high  ranges  in  Colorado  and  the  adjoin- 
ing regions,  are  part  of  the  results.  Probably  at  the  same 
time  the  Cretaceous  strata  of  California,  west  of  the  Sierra 
Nevada,  were  made  into  mountains  that  are  now  part  of 
the  coast  ranges.  This  then  was  one  of  the  great  mountain- 
making  epochs  iii  American  Geological  history. 

In  the  Orient  the  Eocene  era  was  one  of  very  extensive 
submergence  of  the  land,  as  shown  by  the  distribution  of  the 
nummulitic  beds  over  Europe,  Asia,  and  Northern  Africa,  as 
stated  on  page  333.  Before  the  close  of  the  Eocene,  the 
greater  part  of  these  Continental  seas  became  dry  land,  and 
in  general  continued  so  afterward ;  for  the  marine  Miocene  and 
Pliocene  are,  comparatively,  of  limited  extent.  Many  of  the 
great  mountains  of  the  globe,  as  the  Pyrenees,  Alps,  Carpa- 
thians, Himalayas,  etc.,  received  then  a  large  part  of  their 
elevation,  as  is  proved  by  their  containing  Eocene  rocks  in 
their  structure,  or  by  their  bearing  them  about  their  summits. 
Thus  it  is  learned  that  the  elevation  of  the  Pyrenees,  though 
commenced  before  the  close  of  the  Cretaceous,  was  mainly 
produced  in  the  middle  or  later  part  of  the  Eocene,  as  also 
that  of  the  Julian  Alps,  the  Apennines  and  Carpathians,  and 
that  of  heights  in  Corsica.  The  Himalayas,  in  their  western 
part  about  Cashmere,  have  nummulitic  or  Eocene  beds,  at  a 
height  of  16,500  feet ;  so  that  even  this  great  chain,  although 
earlier  elevated  to  the  east,  was  not  completed  before  the 
Middle  Eocene ;  and  even  later  than  this  it  received  a  consid- 
erable part  of  its  elevation,  as  later  Tertiary  beds  at  lower 
levels  show.  The  elevation  of  the  Western  Alps,  including 
Mont  Blanc,  is  referred  by  Elie  de  Beaumont  to  the  close  or 
latter  part  of  the  Miocene  period;  and  that  of  the  Eastern 
Alps,  along  the  Bernese  Oberland,  to  the  close  of  the  Plio- 
cene. An  elevation  of  3,000  feet  took  place  in  Sicily  after 
the  Pliocene. 


QUATERNARY  AGE.  347 

Many  parts  of  the  region  of  the  Andes  were  raised  3,000 
to  5,000  feet  or  more  in  the  course  of  the  Tertiary  period. 

Climate.  —  During  the  Eocene,  Palms  abounded  in  Britain, 
—  evidence  of  a  sub-tropical  or  warm-temperate  climate  in  its 
latitudes;  and  the  Arctic  regions  had  forests  consisting  of 
Beech,  Plantain,  Willow,  Oak,  Poplar,  Walnut,  Magnolia,  Red- 
wood, showing  a  mean  temperature  of  at  least  48°  F.  (Heer.} 
In  the  Miocene,  Southern  Europe  had  a  sub-tropical  climate, 
but  England  had  lost  its  palms  and  was  cooler. 

In  North  America,  the  Eocene  palms  and  other  plants  of 
the  Upper  Missouri  region  show  that  the  temperature  of 
North  Carolina  characterized  then  the  region  of  the  Upper 
Missouri,  the  vicinity  of  the  Great  Lakes,  and  also  Vermont, 
where  exists  the  Brandon  deposit  of  nuts  and  lignite. 

The  Camels,  Rhinoceroces,  and  other  animals  of  the  Pliocene 
of  the  Upper  Missouri,  seem  to  prove  that  a  warm-temperate 
climate  prevailed  there  in  that  closing  epoch  of  the  Tertiary. 

It  is  therefore  plain  that  the  Earth  had  not  as  great  a  diver- 
sity of  zones  of  climate  as  now ;  and  that  Europe  was  little  if 
any  colder  in  the  Eocene  than  in  the  Jurassic  era.  If  the 
interval  between  the  Cretaceous  and  Tertiary  was  one  of  un- 
usual cold,  through  Arctic  and  other  elevations,  as  suggested 
on  page  328,  the  cold  epoch  had  mostly  passed  when  the 
Eocene  era  opened. 

II.   QUATERNARY   AGE,    or   ERA   OP   MAN. 

1.  General  characteristics,  —  The   Quaternary   age  was   re- 
markable (1)  for  high-latitude  movements  and  operations  both 
north  and  south  of  the  equator ;  (2)  for  the  culmination  of  the 
type  of  brute  Mammals ;  and  (3)  for  the  appearance  of  Man  on 
the  globe. 

2.  Periods.  —  The  periods  are  three  :  — 

1.  The  Glacial,  or  the  period  when,  over  the  higher  latitudes, 
the  continents  underwent  great  modifications  in  the  features 
*?  the  surface  through  the  agency  of  ice. 


348  CENOZOIC  TIME. 

2.  The  Champlain,  when  the  ice  disappeared,  and  the  same 
high-latitude  portions  of  the  continent,  and  to  a  less  extent 
the  lower,  were  below  their  present  level,  and  became  covered 
by  extensive  fluvial  and  lacustrine  formations,  and  along  sea- 
coasts  by  marine  formations. 

3.  The  Receni  or  Terrace  period,  begun  by  a  rising  of  the 
land  nearly  or  quite  to  its  present  level. 

I .  Glacial  Period. 

The  following  are  some  of  the  facts,  characterizing  the 
Glacial  period :  — 

1.  Transportation. —  The  transportation  of  a  vast  amount 
of  earth  and  stones  from  the  higher  latitudes  to  the  lower. 

The  transported  material  consists  of  earth,  gravel,  stones, 
and  bowlders,  and  includes,  in  America,  nearly  all  the  earth, 
as  well  as  stones,  of  the  surface  in  the  latitudes  of  New  Eng- 
land and  farther  north.  It  extends  over  hills  and  valleys, 
and  varies  in  depth  from  a  few  feet  to  hundreds.  A  large 
part  of  the  material  is  in  an  unstratifted  condition,  large 
stones  and  small,  pebbles  and  sand,  being  mingled  pell-mell. 
Part,  especially  that  in  the  valleys  or  depressions  of  the  sur- 
face, is  stratified,  and  thus  bears  evidence  of  deposition  by 
flowing  waters,  like  fluvial  and  lacustrine  formations. 

The  transported  material  is  called  Drift,  and  the  unstratified 
part  of  it  till  (from  the  Scotch).  The  till,  especially  its  lower 
part,  is  often  a  clayey  eaith,  or  a  clayey  mixture  of  earth  and 
stones  with  frequent  bowlders,  called  the  bowlder-clay ;  it  is 
in  general  firmly  compacted  because  of  the  clay.  In  the 
valleys  the  clay  is  often  straticulate. 

The  drift-covered  region  of  North  America,  or  that  over 
which  the  great  southward  movement  took  place,  extends 
from  the  Atlantic  border  of  New  England  and  Labrador,  west- 
ward, for  more  than  1,200  miles,  Dakota  and  Lake  Winnipeg 
being  near  the  western  border :  but,  farther  north,  it  extends 
across  the  continent ;  and  along  the  Eocky  Mountains  and 
the  Pacific  border  spreads  southward  again. 


GLACIAL    PERIOD.  349 

The  southern  limit  of  travel  for  the  unstratified  drift,  or 
till,  is  not  fully  made  out.  It  is  supposed  to  have  had  its 
course  from  Cape  Cod  (though  perhaps  lying  miles  outside  of 
it)  to  Long  Island  arid  Perth  Amboy,  N.  J. ;  through  New 
Jersey  northward  and  westward  to  Oxford ;  through  Pennsyl- 
vania to  a  point  north  of  Pittsburg ;  through  Ohio,  by  Dan- 
ville, to  the  Ohio  east  of  Cincinnati ;  thence  for  a  few  miles 
in  Kentucky ;  thence  northwestward  and  westward  through 
Middle  Indiana  and  Illinois,  and- the  States  west,  and  to  have 
included  (Upham)  the  Coteau  de  Missouri  in  Dakota.  The 
stratified  drift  (which  is  mostly  a  deposit  of  the  Champlain 
period,  as  explained  beyond)  occurs  much  farther  south  along 
the  river-valleys,  and  reaches  even  to  the  State  of  Mississippi 
in  the  Mississippi  valley. 

The  travelled  stones  are  of  all  dimensions,  from  that  of  a 
small  pebble  to  masses  as  large  as  a  moderate-sized  house. 
One  at  Bradford  in  Massachusetts  is  30  feet  each  way,  and 
its  weight  is  estimated  to  be  at  least  4,500,000  pounds. 
Many  on  Cape  Cod  are  20  feet  in  diameter.  One  lying  on 
a  naked  ledge  at  Whitingharn  in  Vermont  measures  43  feet 
in  length  and  30  in  height  and  width,  or  39,000  cubic  feet  in 
bulk,  and  was  probably  transported  across  Deerfield  Valley, 
the  bottom  of  which  is  500  feet  below  the  spot  where  it  lies. 
There  are  many  great  bowlders  of  trap  from  50  to  1,250  tons 
in  weight  along  the  western  border  of  the  Triassico-Jurassic 
area  in  Connecticut,  the  line  reaching  to  Long  Island  Sound, 
just  west  of  New  Haven;  and  others  of  great  magnitude 
occur  farther  south  on  Long  Island. 

The  directions  of  travel,  as  learned  by  tracing  the  stones  in 
numerous  cases  to  the  ledges  whence  they  were  derived,  are, 
in  general,  between  southwestward  and  southeastward.  The 
distance  to  which  the  stones  were  transported  in  North  Am- 
erica, as  learned  by  comparing  them  with  the  rocks  in  place 
to  the  north,  is  mostly  between  10  and  40  miles,  though  in 
some  cases  over  200  miles.  The  material  was  carried  south- 
ward across  the  Great  Lakes  and  across  Long  Island  Sound  — 


350 


CENOZOIC   TIME. 


the  land  to  the  south,  in  each  case,  being  covered  with  stones 
from  the  land  to  the  north. 

Besides  this  northern  Drift,  there  are  similar  accumulations 
of  earth  and  stones  belonging  to  the  same  era,  distributed 
locally  about  some  of  the  Appalachian  ridges,  south  of  Drift 
latitudes ;  also  on  a  grand  scale  about  the  higher  ridges  of  the 
summit  of  the  Eocky  Mountains,  and  in  the  Sierra  Nevada 
and  other  ranges  and  heights  of  the  Pacific  border  region. 

Fig.  449. 


Drift  groovings  or  scratches. 

2.  Scratches. — The  rocky  ledges  over  which  the  drift  was 
borne  are  often  scratched,  in  closely  crowded  parallel  lines,  as 
in  the  preceding  figure  (Fig.  449),  and  planed  off  besides.  The 
scratchings  or  groovings  are  sometimes  deep  and  broad  chan- 
nellings,  and  at  times  a  yard  or  more  deep  and  several  feet 
wide,  as  if  made  by  a  tool  of  great  size  as  well  as  power. 
The  scratches  occur  wherever  the  drift  occurs,  provided  the 
underlying  rocks  are  sufficiently  durable  to  have  preserved 
them,  and  they  are  usually  of  great  uniformity  in  any  given 
region.  In  some  places  two  or  more  directions  may  be  ob- 
served on  the  same  surface.  They  are  found  in  the  valleys 
and  on  the  slopes  of  mountains,  to  a  height,  on  the  Green 


GLACIAL    PERIOD.  351 

Mountains,  of  4,400  feet,  and  on  the  White  Mountains  of 
5,500  feet.  They  have  nearly  a  common  course  over  the 
higher  lands  of  a  region,  and  even  cross  slopes  and  the 
smaller  valleys,  without  following  the  direction  of  the  slope 
or  valley;  hut  they  generally  conform  to  the  directions  of 
the  great  valleys  of  the  land,  aad  often  to  the  smaller  when 
they  have  much  breadth.  In  the  Hudson  Elver  Valley,  be- 
tween the  Catskills  and  Green  Mountains,  the  scratches  have 
mostly  the  course  of  the  valley;  and  also  in  the  Connecticut 
River  Valley,  the  Merrimack,  and  other  valleys. 

The  stones,  or  bowlders,  of  the  till  are  often  scratched  as 
well  as  the  rocks,  and  in  this  respect  they  differ  from  those 
of  stratified  drift;  the  latter  have  lost  all  scratches  by  river 
abrasion. 

3.  European  Drift.  —  The  Drift  in  Europe  presents  the  same 
general  course  and  peculiarities  as  in    North  America.      It 
reaches  south  in  some  places  to  about   latitude    50°.     The 
region  south  of  the  Baltic,  and  parts  of  Great  Britain,  are 
covered  with  drift  and  stones  from  Scandinavia.    The  distance 
of  travel  varies  from  5  or  10  miles  to  500  or  600.     About  the 
Alps  and  other  high  mountains  south  of  Drift  latitudes  there 
are  local  accumulations  of  Drift  of  the  Glacial  area,  and  also 
scratches  over  the  surface  rocks. 

4.  Fiords.  —  Fiords  are  deep,  narrow  sea-channels  running 
many  miles  into  the  land.     They  occur  on  the  coasts  of  Nor- 
way, Britain  ;  of  Maine,  Nova  Scotia,  Labrador,  Greenland ; 
on  the  coast  of  Western  North  America  north  of  the  Straits  of 
De   Fuca ;  along  that  of  Western  South  America  south   of 
latitude  41°  S. 

Fiords  are  thus,  like  the  Drift,  confined  to  the  higher  lati- 
tudes of  the  globe,  the  Drift-latitudes ;  and  the  two  may  have 
been  of  contemporaneous  origin. 

5.  Origin  of  the  Drift.  —  Nothing  but  moving  ice  could  have 
transported  the  Drift  with  its  immense  bowlders. 

Glacier  Theory.  —  The  ice  is  performing  this  very  work  now 
in  the  glacier  regions  of  the  Alps  and  other  icy  mountains, 


352  CENOZOIC  TIME. 

and  stones  of  as  great  size  have  in  former  times  been  "borne 
by  a  slow-moving  glacier  from  the  vicinity  of  Mont  Blanc 
across  the  lowlands  of  Switzerland  to  the  slopes  of  the  Jura 
Moun tarns,  and  left  there  at  a  height  of  over  2,000  feet  above 
the  level  of  Lake  Geneva.  Moreover,  there  are  in  many 
places  deposits  of  bowlder-clay,  made  of  the  earth  formed  by 
trittiration  of  stones  against  stones  during  the  moving  of  the 
glacier.  Further,  there  are  scratches,  of  precisely  the  same 
character  as  to  numbers,  depth,  and  parallelism,  on  the  gran- 
itic and  limestone  rocks  of  the  ridges  ;  and  besides,  the  trans- 
ported material  is  left  unstratified  over  the  land,  wherever  it 
is  not  acted  upon  and  distributed  by  Alpine  torrents. 

Icebergs  also  transport  earth  and  stones,  as  in  the  Arctic 
seas ;  and  great  numbers  are  annually  floated  south  to  the 
Newfoundland  banks,  through  the  action  of  the  northern  or 
Labrador  current,  where  they  melt  and  drop  their  great  bowld- 
ers and  burden  of  gravel  and  earth  to  make  deposits  over  the 
sea-bottom.  But  icebergs  could  not  have  covered  great  sur- 
faces so  regularly  with  scratches,  Again,  there  are  no  marine 
relics  in  the  unstratified  drift  to  prove  that  the  continent  was 
under  the  sea  in  the  Glacial  period. 

There  is*  a  seeming  difficulty  in  the  glacier  theory,  from  the 
supposed  want  of  a  sufficient  slope  in  the  surface  to  produce 
movement.  But  a  slope  in  the  under  surface  is  not  needed, 
any  more  than  for  the  flowing  of  pitch.  Pitch,  deposited  in 
continued  supply  on  any  part  of  a  plain,  would  spread  in  all 
directions  around;  and  this  it  would  do  if,  instead  of  a  plain, 
the  surface  beneath  had  an  ascending  slope.  The  slope  of  the 
upper  surface  of  a  plastic  or  fluid  substance  determines  the 
rate  of  flow,  not  that  of  the  under  surface.  Hence,  if  ice  were 
accumulated  over  a  region  so  that  the  upper  surface  had  the 
requisite  slope,  there  would  be  motion  in  the  mass  in  the 
direction  of  this  slope,  whatever  the  bottom  slope  might  be. 
At  the  same  time  the  slope  of  the  land  at  bottom,  or  the  courses 
of  the  valleys,  would  determine  to  some  extent  the  movement 
at  bottom ;  just  as  oblique  grooves  in  a  sloping  board,  down 


GLACIAL   PERIOD.  353 

which  pitch  was  moving,  would  determine  more  or  less  com- 
pletely the  direction  of  the  movement  in  the  grooves. 

A  semi-continental  glacier.  All  the  facts  or  phenomena  con- 
nected with  the  northern  Drift  are  fully  explained  by  refer- 
ence to  a  great  northern  semi-continental  glacier  as  the  cause  ; 
and  those  relating  to  local  Drift  about  high  mountains,  south 
of  Drift  latitudes,  by  referring  them  to  local  glaciers.  But 
icebergs  drifted  down  the  coast,  and  probably  crossed  the 
Hooded  region  of  the  Great  Lakes.  Ice-floes  descended  rivers, 
dropping  their  stones  by  the  way.  On  the  Mississippi,  the 
floating  ice  may  have  reached  the  Gulf  of  Mexico  and  the 
chilled  waters  have  destroyed  much  tropical  life. 

The  height  to  which  scratches  and  drift  occur  about  the 
White  Mountains  proves  that  the  upper  surface  of  the  ice  in 
that  region  was  6,000  or  6,500  feet ;  and  hence  that  the  ice 
was  not  less  than  5,000  feet  thick  over  that  part  of  North- 
ern New  England.  Facts  also  show  that  the  surface  height 
in  southwestern  Massachusetts  was  at  least  2,800  feet;  in 
southern  Connecticut,  1,000  feet  or  more ;  in  the  Catskills, 
3,000  feet  (Smock). 

Since  the  slopes  of  the  upper  surface  of  a  glacier  deter- 
mine the  general  direction  of  movement,  and  therefore  of 
transportation  and  abrasion,  the  lines  of  scratches  or  of  drift 
are  an  indication  as  to  the  position  of  the  ice-summit.  The 
prevailing  direction  over  the  higher  lands  of  New  England 
and  eastern  Canada  is  southeastward,  and  that  over  western 
New  York  and  Pennsylvania  and  the  country  north  and 
northwest  to  Winnipeg  Lake,  is  southwcstward.  The  lines  con- 
sequently converge  northward,  toward  the  part  of  the  Canada 
water-shed  west  of  north  from  Montreal  and  a  region  extend- 
ing thence  northeastward  toward  the  Arctic  regions ;  and 
hence  along  this  course  there  must  have  been  the  summit  of 
a  great  ice  range.  Farther  west,  over  the  dry  interior  of  the 
continent  (where  the  present  amount  of  annual  precipitation 
is  only  12  to  20  inches),  the  ice  thinned  out  or  was  absent. 

It  is  consequently  evident  that  the  ice  of  the  Glacial  era 

23 


354  CENOZOIC  TIME. 

in  America  was  not  an  ample  "  ice-cap  "  covering  the  north- 
ern latitudes  nearly  half  way  to  the  equator,  but  that  the  ice 
stretched  southward  from  a  polar  area  along  the  courses  of 
greatest  atmospheric  precipitation ;  which  courses  were  three 
in  number :  one  of  great  width  and  height  on  the  Atlantic 
side,  the  moist  side  of  the  continent ;  a  second,  of  compara- 
tively narrow  limits,  on  the  Pacific  side ;  and  a  third,  follow- 
ing the  higher  ridges  of  the  Rocky  Mountains. 

The  stones  and  earth  transported  by  the  Continental  glacier 
were  gathered  up  mostly  by  its  lower  part,  from  the  surface 
of  hills  or  ridges  that  projected  into  it,  and  even  from  the 
plains  beneath  it.  In  New  England,  where  there  were  no 
peaks  rising  above  the  upper  surface  to  be  a  source  of  aval- 
anches, as  in  the  Alps,  many  of  the  masses  thus  taken  aboard 
exceed  1,000  tons  in  weight. 

-Excavating  action  of  the  Glacier.  — With  a  thickness  of 
even  2,000  feet  the  glacier  would  have  had  great  excavating 
force,  although  the  abrading  power  was  not  great.  Soft 
rocks  would  have  been  deeply  ploughed  up  by  it,  and  all 
jointed  and  fissile  rocks,  soft  or  hard,  would  have  been  torn 
to  fragments,  and  the  loosened  masses  borne  off.  By  this 
means,  and  most  of  all  through  the  erosion  of  subglacial 
streams,  valleys  were  excavated  and  widened. 

Drift  in  other  Countries.  — The  drift  phenomena  of  Europe 
lead  to  the  same  general  conclusion :  that  amount  of  precipi- 
tation determined  to  a  large  extent  the  distribution  of  the  ice ; 
temperature  being  the  other  chief  condition.  The  southern 
limit  is,  on  an  average,  10°  higher  in  latitude  in  Europe  than  in 
America,  corresponding  to  the  modern  fact  as  to  the  climate 
of  the  region.  The  great  European  ice-range  followed  the 
course  of  the  Scandinavian  mountains,  the  moist  mountain- 
border  of  Western  Europe.  The  Alps,  although  outside  of 
the  area  of  northern  drift,  had  glaciers  over  2,000  feet  above 
their  present  limit ;  and  enormous  bowlders  from  the  Alps 
(one  of  3,000  tons)  lie  high  on  the  Juras,  to  the  west  of  the 
plains  of  Switzerland.  With  such  facts  from  the  Alps,  large 


GLACIAL  PERIOD.  355 

estimates  as  to  the  thickness  of  the  ice  in  America  lose  their 
apparent  extravagance.  In  Asia  the  precipitation  was  too 
small  to  make  a  glacier  over  the  lower  plains. 

Greenland  is  at  the  present  time  a  glaciated  continent, 
nearly  as  northern  America  was  in  the  Glacial  era.  The  ice 
moves  where  the  slope  of  surface  is  less  than  half  a  degree. 
In  the  Glacial  era,  the  Greenland  ice  stood,  in  some  parts  of 
the  Coast  region,  3,000  feet  above  its  present  level ;  which  is  a 
small  difference  compared  with  the  thickness  of  ice  produeed 
by  the  Glacial  era  in  more  southern  and  moister  latitudes. 

On  the  possible  origin  of  a  yladal  climate,  see  page  125. 

2.  Champiain  Period. 

The  Champiain  period,  as  is  proved  by  marine  relics  and  by 
other  facts  described  beyond,  was  an  era  of  depression  in  the 
continents  over  the  higher  latitudes  below  the  present  level,  and 
a  depression  which,  within  certain  limits,  increased  to  the 
northward.  It  was  also  a  period,  as  indicated  by  the  terres- 
trial life,  of  warmer  climate  than  the  Glacial ;  and,  probably, 
because  of  the  lower  level  of  the  northern  or  high-latitude 
lands.  The  warmer  climate  appears  to  have  determined  the 
melting  of  the  great  glacier,  and  it  caused  this  melting  to  go  on 
widely  over  its  surface ;  so  that,  when  it  had  thinned  down 
the  ice  to  within  500  or  1,000  feet,  the  disappearance  of  the 
rest  of  the  ice  went  forward  with  accelerated  progress. 

(1)  The  melting  was  thus  the  great  event  of  the  opening 
part  of  the  Champiain  period ;  and  it  must  have  caused  im- 
mense floods  in  all  valleys,  vastly  beyond  those  from  the 
breaking  up  of  an  ordinary  winter. 

With  the  melting  of  the  lower  1,000  feet,  and  during  the 
era  of  floods,  there  would  have  been  (2)  the  deposition  of  the 
earth,  gravel,  and  stones  contained  therein ;  and  in  the  de- 
position, wherever  the  material  fell  over  the  land,  it  would 
have  gone  down  pell-mell  and  been  left  (a]  unstratified ;  while, 
whatever  fell  into  flowing  streams,  lakes,  tidal  estuaries,  or 
along  sea-coasts,  would  have  been  (V)  stratified.  The  stratified 


356  CENOZOIC  TIME. 

deposits  of  the  Champlain  period  are  then  either  (1)  of  river- 
valley  origin,  (2)  lacustrine,  or  (3)  estuary  or  marine. 

After  the  era  of  floods  or  the  Diluvial  part  of  the  Champlain 
period,  the  depositions  in  what  may  be  called  the  Alluvial 
part  of  the  period  went  on  more  quietly;  and  many  land 
shells,  bones,  and  other  relics  are  contained  in  the  river- 
valley  deposits  then  made. 

The  Diluvial  beds  consist  of  earth,  clay,  sand  or  pebbles, 
or  of  mixtures  of  these  materials.  And  the  Alluvial  are  partly 
the  same,  but  more  commonly  of  finer  earth  and  clay. 

The  river-border  deposits  occur  in  all  or  nearly  all  the 
river- valleys  within  the  drift  latitudes  of  the  North  American 
continent,  from  Maine  to  Oregon  and  California;  and  they 
exist  farther  south,  extending  along  the  Mississippi  Valley  to 
the  Gulf  of  Mexico.  The  cold  water  descended  the  valley  in 
a  vast  flood  to  the  Gulf,  bearing  on  its  surface  much  drift  ice 
from  the  dissolving  glacier,  —  the  fact  of  the  flood  and  that 
of  the  floating  ice  being  proved,  as  Hilgard  has  shown,  by  the 
nature  of  the  stratified  deposits,  and  the  occurrence  of  northern 
bowlders,  100  to  150  pounds  in  weight  at  least,  as  far  south 
as  the  State  of  Mississippi.  Facts  prove  also  that  the  cold 
waters  and  ice  in  the  Gulf  were  destructive  to  the  tropical 
life  along  its  northern  borders. 

These  river- valley  deposits  form  at  present  elevated  plains 
on  one  or  both  sides  of  the  valley.  Their  elevation  above  the 
river  is  greater  in  Northern  New  England  than  in  Southern ; 
and  there  is,  in  general,  a  like  difference  between  those  of  the 
northern  and  southern  parts  of  the  States  west  of  New  Eng- 
land ;  this  height,  in  valleys  remote  from  the  coast,  is  mainly 
due  to  the  height  of  the  flood. 

The  view  in  Fig.  450  represents  a  scene  on  the  Connecti- 
cut, a  few  miles  below  Hanover  in  New  Hampshire,  where 
there  are  three  different  levels,  or  terraces,  in  the  alluvial 
formation ;  the  upper  shows  the  total  thickness  of  the  for- 
mation down  to  the  river-level. 

As  the  Glacial  flood  declined,  the  waters  gradually  fell  below 


QUATERNARY  AGE. 


357 


the  top  of  the  flood-made  valley  formation,  and  in  most  cases 
far  below  it,  leaving  it  as  a  high  terrace  plain,  with  sometimes 
one  or  more  lower  terraces  (Fig.  450).  The  lower  terraces 
may  have  been  made  by  changes  in  the  river  as  it  subsided ; 
or  they  may  be  only  different  levels  of  the  bottom  of  the  great 
Hooded  stream,  like  the  Hats  at  different  depths  in  any  broad 
river  or  bay.  The  main  channel  of  the  flooded  stream  was 

Fig.  450. 


Terraces  on  the  Connecticut  River,  south  of  Hanover,  N.  H. 

kept  large  and  deep  where  the  flow  along  the  valley  was  most 
violent,  and  less  deep  where  less  violent.  Terraces  have  often 
great  height  above  a  narrow  gorge,  because  the  waters  were 
there  dammed  by  floating  ice  or  other  means. 

Terraces  in  river-valleys  have  sometimes  resulted  from  an 
elevation  of  the  land,  this  giving  a  stream  greater  pitch,  and 
hence  causing  an  excavation  of  its  bed  to  a  lower  level.  But 
examples  of  such  are  mostly  confined  to  the  parts  of  river- 
valleys  toward  the  sea-coast. 

In  many  places,  the  upper  part  of  the  terrace  formation, 
for  10  to  40  feet,  is  coarsely  stony,  while  underneath  it  usu- 
ally consists  of  sandy,  pebbly,  or  clayey  layers.  This  over- 
lying coarse  bed  shows  that  the  flood,  toward  the  close  of  the 


358  CENOZOIC  TIME. 

glacier,  was  suddenly  augmented  in  depth  and  violence.  Such 
coarse  beds  occur  where  the  now  was  most  violent,  and  they 
often  top  one  of  the  lower  terraces,  these  being  low  because  of 
the  violence  of  the  flow  over  them. 

The  lacustrine  deposits  are  of  similar  character  to  those  of 
the  valleys,  and  of  like  distribution  over  the  continent ;  and 
they  are  equally  elevated  above  the  present  level  of  the  water 
they  border. 

The  sea-border  deposits,  or  those  formed  on  sea-shores  and 
estuaries,  are  found  at  many  places  on  the  coasts  of  New  Eng- 
land, both  the  southern  and  eastern.  At  several  localities  in 
Maine  they  afford  shells  at  heights  not  far  from  200  feet 
above  the  sea-level.  They  form  deposits  of  great  thickness 
along  the  St.  Lawrence,  as  near  Quebec,  Montreal,  and  King- 
ston ;  at  Montreal  they  contain  numerous  marine  shells  at  a 
height  of  400  to  520  feet  above  the  river.  They  border  Lake 
Champlain,  being  there  393  feet  in  height  above  its  level ; 
and,  besides  marine  shells,  the  remains  of  a  whale  have  been 
taken  from  the  beds. 

In  the  Arctic  regions  similar  deposits  full  of  shells  are 
common,  at  different  elevations  up  to  600  or  800  feet,  and  in 
some  places  1,000  feet,  above  the  sea-level. 

These  sea-border  deposits,  now  elevated,  must  have  been  at 
the  water-level,  or  below  it,  when  they  were  formed ;  that  is, 
in  the  Champlain  period.  The  facts  prove  that  the  river  St. 
Lawrence  was  at  that  time  an  arm  of  the  sea,  of  great  breadth, 
with  the  bordering  land  400  to  500  feet  lelow  its  present  level; 
that  Lake  Champlain  was  a  deep  lay  opening  into  the  St.  Law- 
rence channel,  and  that  it  had  its  whales  and  seals  as1  well  as 
sea-shells  ;  that  the  coast  of  Maine  was  in  part  200  feet  belov/ 
its  present  level,  and  Southern  New  England  10  feet. 

There  is  some  reason  for  the  opinion  that  the  whole  north- 
ern portion  of  the  continent  was  less  elevated  than  now ;  and 
abo  that  the  depression  was  greatest  to  the  north,  since  the 
sea-border  Champlain  formations  on  both  the  Atlantic  and 
Pacific  sides  are  above  the  present  sea-level,  and  at  higher 


QUATERNARY  AGE.  359 

elevations  to  the  north,  or  near  the  northern  boundary  of  the 
United  States,  than  they  are  to  the  south. 

The  facts  here  stated  with  regard  to  elevated  river- valley, 
lacustrine,  and  sea-border  formations  in  North  America  have 
their  parallel  in  Europe.  In  Great  Britain  the  Glacial  period 
was  followed  by  one  of  depression,  in  which  its  northern  por- 
tions were  over  1,000  feet  below  their  present  level.  The  re- 
markable terraces  or  benches  of  Glen  Eoy,  in  Scotland,  are 
three  in  number,  and  1,139,  1,039,  and  847  feet  above  the 
sea-level.  In  Sweden  there  are  sea- border  beds  with  shells 
very  similar  to  those  of  Maine  and  the  St.  Lawrence ;  and 
facts  prove  that  the  White  Sea  was  then  connected  with  the 
Baltic,  and  possibly  with  the  Caspian. 

While,  therefore,  the  facts  relating  to  the  Glacial  period 
favor  the  view  that  the  northern  portions  of  the  continents 
were  then  raised  above  their  present  level,  those  of  the  next  or 
Champlain  period  suggest  that  they  were  afterward  beloiv 
their  present  level.  If  so,  there  was  an  upward  high-latitude 
movement  for  the  Glacial  period  and  a  downward  for  the 
Champlain  period;  and  the  latter  movement  brought  to  its 
close  the  era  of  ice,  by  occasioning  a  warm  climate. 

3.    Recent  Period. 

When  the  Champlain  period  was  in  progress,  the  upper 
plain  of  the  sea-border  formations,  now  so  elevated,  was  at 
the  sea-level ;  and  the  high  alluvial  plains  along  the  rivers 
were  the  flood-grounds  of  the  rivers.  The  land  has  since  been 
raised ;  and,  consequently,  the  sea-border  formations  are  now 
high  above  tide-level.  Some  of  them  were  of  beach  origin, 
and  the  height  of  these  equals  nearly  the  amount  of  eleva- 
tion; others  were  submerged  mud-banks  or  sea-bottoms,  as 
proved  by  their  fossils,  and  these  were  carried  up  to  a  less 
height  above  the  sea,  according  to  their  depth  beneath  its  sur- 
face. The  formations  thus  elevated  often  make  a  series  of 
terraces  or  "  benches  "  alon^  a  coast. 

O 

The  elevation  also  led  the  rivers  over  the  elevated  region, 


360  CENOZOiC   TIME. 

especially  toward  the  coast,  to  erode  their  beds  through  the 
Champlain  deposits  of  the  valley  to  a  lower  level,  and  so  make 
terraces  on  one  or  both  sides,  as  represented  in  Fig.  451.  But 
the  terraces  over  the  continent  away  from  the  coasts  may  be 
mainly  due  (p.  357)  to  the  subsiding  of  the  waters  after  the 
Hood  was  at  iU,  height  and  had  done  its  chief  work  of  deposi- 
tion, and  only  slightly,  where  at  all,  to  this  elevation. 

Fig.  451. 


Section  of  a  valley  with  its  terraces  completed. 

As  already  stated,  the  sea-border  formations  of  both  sides 
of  the  continent  are  raised  high  above  existing  tide-level,  and 
most  so  to  the  north.  Hence,  while  the  Champlain  period  was 
one  of  a  low  level  in  the  continent,  especially  at  the  north 
(certainly  along  its  coasts,  and  probably  over  its  whole 
breadth),  the  Recent  period  began  in  a  rising  again,  until 
the  region  before  depressed  reached  its  present  height ;  and 
this  rising  was  greatest  at  the  north.  It  is  hence  probable  that 
there  were  high-latitude  oscillations  in  this  part  of  geological 
history  —  an  upward  movement  in  the  Glacial  period,  a  down- 
ward in  the  Champlain  period,  an  upward  again  in  the  Recent 
period ;  but  how  far  such  changes  were  general  over  the  hem- 
isphere is  unknown.  It  does  not  appear  that  the  movement 
resulted  anywhere  in  the  raising  of  a  mountain-range. 

In  Europe  there  was  a  second  Glacial  era,  in  which  the 
njrtharu  portions  of  that  continent  were  again  covered  with 
ice,  and  glaciers  spread  anew  from  the  Alps  over  part  of  LowTer 
Switzerland.  It  appears  to  have  occurred  at  the  close  of  the 
Champlain  period,  and  to  have  been  connected  witli  the  ris- 
ing of  the  land  that  introduced  the  Recent  period,  —  the 
rising  having  carried  the  land  above  its  present  level.  Proofs 


QUATERNARY   AGE.  361 

of  the  occurrence  of  such  an  epoch  are  found  in  the  remains 
of  the  Eeindeer  and  other  sub-arctic  animals,  in  Southern 
France  (page  369),  in  deposits  that  are  subsequent  in  date  to 
true  Champlain  deposits. 

The  Eecent  period  is,  hence,  opened  by  this  second  Glacial 
epoch,  while  it  closes  with  the  modern  or  historical  era. 

Modern  Changes  of  Level. 

The  sea,  the  rivers,  the  winds,  and  all  mechanical  and 
chemical  forces  are  still  working  as  they  have  always  worked ; 
and,  too,  the  earth  is  undergoing  changes  of  level  over  wide 
areas,  although  it  has  beyond  question  reached  an  era  of  com- 
parative repose. 

These  changes  of  level  are  either  paroxysmal,  —  that  is, 
take  place  through  a  sudden  movement  of  the  earth's  crust 
as  sometimes  happens  in  connection  with  an  earthquake ;  or 
they  are  secular,  —  that  is,  result  from  a  gradual  movement 
prolonged  through  many  years  or  centuries.  The  following 
are  some  examples  :  — 

1.  Paroxysmal  —  In  1822  the  coast  of  Western  South 
America,  for  1,200  miles  along  by  Concepcion  and  Valparaiso, 
was  shaken  by  an  earthquake,  and  it  has  been  estimated  that 
the  coast  near  Valparaiso  was  raised  at  the  time  3  or  4  feet. 
In  1835,  during  another  earthquake  in  the  same  region,  there 
was  an  elevation,  it  is  stated,  of  4  or  5  feet  at  Talcahuano, 
which  was  reduced  after  a  while  to  2  or  3  feet.  In  1819 
there  was  an  earthquake  about  the  Delta  of  the  Indus,  and 
simultaneously  an  area  of  2,000  square  miles,  in  which  the 
fort  and  village  of  Sindree  were  situated,  sunk  so  as  to  be- 
come an  inland  sea,  with  the  tops  of  the  houses  just  out  of 
water ;  and  another  region  parallel  with  the  sunken  area,  50 
miles  long  and  in  some  parts  10  broad,  was  raised  10  feet 
above  the  delta.  These  few  examples  all  happened  within 
an  interval  of  sixteen  years.  They  show  that  the  earth  is 
still  far  from  absolute  quiet,  even  in  this  its  finished  state. 


362  CENOZOIC  TIME. 

2.  Secular,  —  Along  the  coasts  of  Sweden  and  Finland,  on 
the  Baltic,  there  is  evidence  that  a  gradual  rising  of  the  land 
is  in  slow  progress.  Marks  placed  along  the  rocks  by  the 
Swedish  government,  many  years  since,  show  that  the  change 
is  slight  at  Stockholm,  but  increases  northward,  and  is  felt 
even  at  the  North  Cape,  1,000  miles  from  Stockholm.  At 
Uddevalla  the  rate  of  elevation  is  equivalent  to  3  or  4  feet  in 
a  century. 

In  Greenland,  for  600  miles  from  Disco  Bay,  near  69°  N.. 
to  the  frith  of  Igaliko  60°  43'  N.,  a  slow  sinking  has  been 
going  on  for  at  least  four  centuries.  Islands  along  the  coast, 
and  old  buildings,  have  been  submerged.  The  Moravian  set- 
tlers have  had  to  put  down  new  poles  for  their  boats,  and 
the  old  ones  stand  "as  silent  witnesses  of  the  change." 

It  is  believed  also  that  a  sinking  is  in  progress  along 
the  coast  of  New  Jersey,  Long  Island,  and  Martha's  Vine- 
yard, and  a  rising  in  different  parts  of  the  coast-region  be- 
tween Labrador  and  the  Bay  of  Fundy.  There  are  deeply 
buried  stumps  of  forest-trees  along  the  sea-shore  plains  of 
New  Jersey,  and  other  evidences  of  a  change  of  level  (G.  H. 
Cook.) 

The  above  cases  illustrate  movements  by  the  century,  or 
those  slow  oscillations  which  have  taken  place  through  the 
geological  ages,  raising  and  sinking  the  continents,  or  at 
least  changing  the  water-line  along  the  land. 

This  fact  is  to  be  noted,  that  these  secular  movements  of 
modern  time  over  the  continents  are,  for  the  most  part,  so  far 
as  observed,  high-latitude  oscillations,  just  as  they  were  in  the 
earlier  part  of  the  Quaternary. 

Life  of  the  Quaternary. 

The  invertebrate  animals  of  the  Quaternary,  and  probably 
also  the  plants,  were  very  nearly  if  not  quite  all  identical 
with  existing  species.  The  shells  and  other  invertebrate 
remains  found  in  the  beds  on  the  St.  Lawrence,  Lake  Cham- 


QUATERNARY   AGE.  — ANIMAL  LIFE.  363 

plain,  and  on  the  coast  of  Maine,  are  similar  to  those  now 
found  on  the  coast  of  Maine  or  Labrador,  or  farther  north. 

The  life  of  the  Quaternary  of  greatest  interest  is  the  Mam- 
malian, which  type,  as  regards  brutes,  culminated  in  the 
Champlain  period.  This  culmination  was  manifested  in  — 
(1)  the  number  of  species,  (2)  the  multitude  of  individuals, 
(3)  the  magnitude  of  the  animals,  —  the  period  in  each  of 
these  particulars  exceeding  the  present  time. 

Along  with  the  brute  Mammals  of  the  Quaternary  ap- 
peared also  Man. 

I.  Brute  Mammals. 

1.  Europe  and  Asia.  —  The  bones  of  Mammals  are  found  in 
caves  that  were  their  old  haunts;  in  Drift  and  stratified 
Champlain  deposits  along  rivers  and  lakes;  in  sea-border 
deposits ;  in  marshes,  where  the  animals  were  mired ;  in  ice, 
preserved  from  decay  by  the  intense  cold. 

The  caves  in  Europe  were  the  resort  especially  of  the 
Great  Cave-Bear  (Ursus  spelceus),  and  those  of  Britain  of  the 
Cave-Hyena  (Hycena  spelcea).  Into  their  dens  they  dragged 
the  carcasses  or  bones  of  other  animals  for  food,  so  that  relics 
of  a  large  number  of  species  are  now  mingled  together  in 
the  earth,  or  stalagmite,  which  forms  the  floor  of  the  cavern. 
In  a  cave  at  Kirkdale,  England,  portions  of  a  very  large  num- 
ber of  Hyenas  have  been  made  out,  besides  remains  of  an 
Elephant,  Lion,  Tiger,  Bear,  Wolf,  Fox,  Hare,  Weasel,  Rhi- 
noceros, Horse,  Hippopotamus,  Ox,  Deer,  and  other  species,  all 
then  inhabitants  of  that  country.  A  cave  at  Gaylenreuth  is 
said  to  have  afforded  fragments  of  at  least  800  individuals  of 
the  Cave-Bear.  The  Cave-Hyena  is  regarded  as  a  large 
variety  of  the  Hyoena  crocuta  of  South  Africa,  and  the  Cave 
Lion,  a  variety  of  Felis  leo,  the  Lion  of  Africa.  But  many  of 
the  species  are  now  extinct. 

The  fact  that  the  numbers  of  species  and  of  individuals  in 
the  Quaternary  was  greater  than  now,  may  be  inferred  from 
comparing  the  fauna  of  Quaternary  Great  Britain  with  that 


364 


CENOZOIC  TIME. 


of  any  region  of  equal  area  in  the  present  age.  The  species 
included  gigantic  Elephants,  two  species  of  Rhinoceros,  a  Hip- 
popotamus, three  species  of  Oxen,  two  of  them  of  colossal  size, 
the  Irish  Deer  (Megaceros  Hibernicus),  whose  height  to  the 
summit  of  its  antlers  was  10  to  11  feet,  and  the  span  of 
whose  antlers  was  in  some  cases  12  feet,  Deer,  Horses,  Wild 
Boars,  a  Wild-cat,  Lynx,  Leopard,  a  Tiger  larger  than  that  of 
Bengal,  a  large  Lion  called  a  Machcerodus,  having  sabre-like 
canines  sometimes  eight  inches  long,  the  Cave-Hyena,  Cav&* 
Bear,  besides  various  smaller  species. 

Fig.  452. 


Skeleton  of  Mastodon  giganteus. 

The  Elephant  (Elcphas  primigcnius)  was  nearly  a  third 
taller  than  the  largest  modern  species.  It  roamed  over 
Britain,  Middle  and  Northern  Europe,  and  Northern  Asia, 
even  to  its  Arctic  shores.  Great  quantities  of  tusks  have 
been  exported  from  the  borders  of  the  Arctic  sea  for  ivory. 


QUATERNARY  AGE.  — ANIMAL  LIFE.  365 

These  tusks  sometimes  have  a  length  of  12£  feet.  Near  the 
beginning  of  the  century  one  of  these  Elephants  was  found 
frozen  in  ice  at  the  mouths  of  the  Lena ;  and  it  was  so  well 
preserved  that  Siberian  dogs  ate  of  the  ancient  flesh.  Its 
length  to  the  extremity  of  the  tail  was  16  J  feet,  and  its 
height  9-J  feet.  It  had  a  coat  of  long  hair.  But  no  amount 
of  hair  would  enable  an  Elephant  now  to  live  in  those  bar- 
ren, icy  regions,  where  the  mean  temperature  in  winter  is 
40°  F.  below  zero.  Siberia  had  also  a  hairy  Rhinoceros. 

Although  there  were  many  Herbivores  among  the  Qua- 
ternary species  of  the  Orient,  the  most  characteristic  animals 
were  the  great  Carnivores.  The  period  was  the  time  of  tri- 
umph of  brute  force  and  ferocity,  and  the  Orient  was  espe- 
cially the  scene  of  its  triumph. 

2.  North  America,  —  In  the  Champlain  period  there  were 
great  Elephants  and  Mastodons,  Oxen,  Hordes,  Stays,  Beavers, 
and  some  Edentates,  in  Quaternary  North  America,  unsur- 
passed in  magnitude  by  any  in  other  parts  of  the  world. 
Herbivores  were  the  characteristic  type.  Of  Carnivores  there 


Fig   453. 


Megatherium  Cuvieri  (  X  TV-r 


were  comparatively  few  species  ;  no  true  cavern  species  have 
been  discovered.  Fig.  452  (from  Owen)  represents  the  speci- 
men of  the  American  Mastodon  now  in  the  British  Museum. 


366  CENOZOIC   TIME. 

The  skeleton  set  up  by  Dr.  Warren  in  Boston  has  a  height 
of  11  feet  and  a  length  to  the  base  of  the  tail  of  17  feet. 
It  was  found  in  a  marsh  near  Newburgh,  New  York.  The 
American  Elephant  was  fully  as  large  as  the  Siberian. 

3.  South  America,  —  South  America  had,  at  the  same  time, 
its  Carnivores,  its  Mastodons,  and  other  Herbivores;  but  it 
was  most  remarkable  for  its  Edentates,  or  animals  related  to 
the  Sloths. 

Fig.  453  shows  the  form  and  skeleton  of  one  of  these 
animals,  —  the  Megath&re.  It  exceeded  in  size  the  largest 
Rhinoceros :  a  skeleton  in  the  British  Museum  is  18  feet 
long.  It  was  a  clumsy,  sloth-like  beast,  but  exceeded  im- 
mensely the  modern  Sloth  in  its  size.  Another  kind  of 
Edentate  had  a  shell  like  a  turtle,  and  was  somewhat  re- 
lated to  the  Armadillo.  One  of  them  is  called  a  Glyptodon 
(Fig.  454).  The  animals  of  this  kind  were  also  gigantic,  the 
Glyptodon  here  figured  having  had  a  length,  to  the  extrem- 
ity of  the  tail,  of  nine  feet. 

South  America  was  eminently  the  continent  of  Edentates. 

Fig.  454. 


Glyptodon  clavipes 


4.  Australia.  —  Quaternary  Australia,  in  the  Champlain 
period,  contained  Marsupial  animals  almost  exclusively,  like 
modern  Australia  ;  but  these  partook  of  the  gigantic  size  so 
characteristic  of  the  Mammalian  life  of  the  period.  One 
species,  called  Diprotodon,  was  as  large  as  a  Hippopotamus, 
and  another,  the  Nototherium.  was  as  large  as  an  ox. 


QUATERNARY  AGE.  — MAN.  367 

5.  Conclusions.  —  The  facts  sustain  the   following   conclu- 
sions :  — 

1.  The  Champlain  period  of  the  Quaternary  was  the  cul-j 
minant  time  of  Mammals,  both  as  to  numbers  and  magni- 
tude. 

2.  Each  continent  was  gigantic  in  that  type  of  Mammalian 
life  which  is  now  eminently  characteristic  of  it :  The  Orient, 
in  Carnivores,  and,  it  may  be  added,  also  in  Monkeys ;  North 
America,  in  Herbivores  ;  South  America,  in  Edentates  ;  Aus- 
tralia, in  Marsupials. 

3.  The  climate  of  Great  Britain  and  Europe,  where  were 
the  haunts  of  Lions,  Tigers,  Hippopotamuses,  etc.,  must  have 
been  warmer  than  now,  and  probably  not  colder  than  warm- 
temperate.    The  climate  of  Arctic  Siberia  was  such  that  shrubs 
could  have  grown  there  to  feed  the  herds  of  Elephants,  and 
hence  could  not  have  been  bcloiv  sub-frigid,  for  which  degree  of 
cold  it  is  possible  the  animals  might  have  been  adapted  by 
their  hairy  covering. 

4.  The  Champlain  period,  the  meridian  time  of  the  Quater- 
nary Mammals,  was  hence,  as  before  stated,  one  of  warmer 
climate  over  the   continents   than   the   present,  and   much 
warmer  than  that  of  the  Glacial  period.     The  species  may 
have  begun  to  exist  before  the  Glacial  period  ended  in  Eu- 
rope ;    but  they  belonged  pre-eminently  to  the  Champlain 
period,  when  the  sinking  of  the  land  over  the  higher  latitudes 
had  introduced  the  warmer  climate. 

5.  The  larger  part  of  the  great  Mammals  of  the  Quater- 
nary disappeared  with  the  close  of  the  Champlain  period  or 
in  the  early  part  of  the  Recent  period,  while  others  found 
refuge  in  the  tropics.     They  were  animals  of  a  warmer  cli- 
mate than  now  belongs  to  the  regions  which  they  then  inhab- 
ited ;  and  the  cold  of  the  second  Glacial  era,  with  which  the 
Recent  period  opened,  probably  brought  about  the  extermina- 
tion and  forced  migration. 

Such  an  epoch  of  cold  could  not  have  been  passed  through 
by  Europe  without  some  refrigeration  of  the  climate  of  N@rth 


368  CENOZOIC  TIME. 

America,  since  the  two  continents  are  bound  together  by  a 
common  Arctic.  The  remains  of  Reindeers  have  been  found 
in  Southern  New  York  and  near  New  Haven  in  Connecticut ; 
but  the  latter,  at  least,  were  found  in  Champlain  deposits,  and 
are  no  evidence  as  to  a  second  Glacial  epoch. 

Among  the  Mammals  of  Europe  which  existed  before  the 
close  of  the  Champlain  period,  some  are  now  living ;  as  the 
Eeindeer,  Marmot,  Ibex,  Chamois,  Elk,  Wild  Boar,  Goat,  Stag, 
Aurochs,  Urus,  Wolf,  Brown  Bear,  and  others. 

2.  Man. 

1.  Relics  of  Man.  —  The  earliest  relics  of  Man  in  Europe 
are  rude  flint  implements,  as  arrow-heads,  chisels,  etc. ;  flint- 
chippings,  or  the  chips  thrown  off  in  making  the  implements ; 
rude  carvings ;  human  bones  and  skeletons  ;  the  bones  of  the 
animals  used  for  food,  split  lengthwise,  this  being  done  to  get 
at  the  marrow ;  charcoal,  and  other  remains  of  fires.     They 
occur  associated  with  the  remains  of  the  Cave-Bear,  Cave- 
Hyena,  Cave-Lion,  Elephant,  and  other  species.     They  date 
from  the  Champlain  period,  and  perhaps,  in  part,  from  the 
earlier  Glacial  period. 

2.  The  Paleolithic  Era,  —  As  the  only  implements  of  early 
Man  in  Europe  were  of  stone,  the  era  in  human  history  has 
been  called  the  "  Stone  age  "  ;  and  this  earliest  part  of  that 
age,  above  referred  to,  has   been  designated  the  Paleolithic 
era,  from  the  Greek  TraXato?,  ancient,  and  X/#o?,  stone.     Por- 
tions of  skeletons  referred  to  this  era  have  been  found  in 
Belgium,  and  some  other  countries.     The  Belgian  skulls  are 
"  fair  average  skulls  "  ;  "  the  lowest  yet  discovered  cannot  be 
regarded,"  says  Huxley,  as  "  the  remains  of  a  human  bei no- 
intermediate  between  Man  and  the  Apes."     The  stone  imple- 
ments are  never  polished,  and  are  of  ruder  make  than  those 
of  the  later  part  of  the  Stone  age. 

3.  The  Reindeer  Era.  —  The  second  section  of  the  European 
Age  of  Stone  has  been  called  the  Reindeer  era.     It  was  the 
time  of  the  second  Glacial  epoch,  and  it  is  distinguished  by 


QUATERNARY  AGE.  —  MAN.  369 

the  occurrence  of  large  numbers  of  the  bones  01  the  Rein- 
deer  in  the  caves  of  Southern  France,  along  with  the  human 
relics.  The  flint  implements  of  this  era  are  well  made,  but  un- 
polished ;  and  among  the  relics  there  are  implements  of  bone 
or  horn,  and  drawings  of  animals  upon  these  materials.  One 
of  these  drawings  from  Southern  France,  made  on  ivory,  is 
copied  in  Fig.  455.  It  represents  the  hairy  Elephant  of  the 


455. 


Elephas  primigenius  ;  engraved  in  ivory  ( X  f ). 

era.  Remains  of  the  Elephant,  Cave-Bear,  Cave-Hyena,  Cave- 
Lion,  occur  in  the  same  deposits,  and  also  others  of  existing 
species,  as  the  Elk,  Ibex,  Aurochs,  Urus,  etc.  Perfect  skele- 
tons of  man  have  been  found  in  some  of  the  caverns.  Those 
of  Southern  France  are  in  part  of  tall  size,  —  5  feet  9  inches 
to  6  feet,  —  having  well-shaped  heads,  and  a  large  facial  angle 
(85°).  One,  from  a  cave  at  Mentone  (on  the  Mediterranean 
near  the  borders  of  France  and  Italy),  was  of  a  man  full  6  feet 
in  height ;  and  it  lay  buried  in  the  stalagmite  of  the  cave, 
with  flint  implements  and  shell  ornaments  around,  and  a 
chaplet  of  stag's  teeth  across  its  head. 

4.  The  Neolithic  Era.  —  A  third  era  is  named  the  Neolithic 
(from  z/eo?,  new,  arid  \i0os).  The  relics  are  polished  stone  im- 
plements, broken  pottery,  bones  of  the  dog.  All  remains  of 
extinct  Champlain  Mammals  and  the  Reindeer  are  absent. 
The  race  of  men  in  Denmark  resembled  the  Laplanders. 

24 


370 


CENOZOIC   TIME. 


To  later  time  in  this  era  belong  the  earlier  "lake-dwellings  " 
of  Switzerland,  —  structures  built  on  piles  in  the  lakes  —  in 
which  the  only  implements  are  of  stone.  But  in  the  later, 
about  the  western  Swiss  lakes,  there  are  bronze  implements, 
and  these  are  of  the  "  Bronze  age." 

In  America,  rude  stone  implements  have  been  found  (first 
by  C.  C.  Abbot)  in  the  stratified  gravel  near  Trenton,  N.  J., 
which  has  afforded  also  Mastodon  bones;  testifying  to  the 
existence  there  of  Man  in  the  Chainplain  period,  if  not  in 
the  Glacial.  The  human  skull  reported  from  ancient  gravels 
of  Calaveras  County,  California,  is  still  of  doubted  antiquity, 
and  partly  because  so  like  a  modern  Indian's  skull. 

5.  Modern  Human  Relics.  —  In  still  later  deposits,  buried 
coins,  statues,  temples,  cities,  are  found  among  the  earth's 
fossils,  contrasting  strangely  with  the  remains  of  the  species 


Figs   456,  457. 


456 


Iluman  skeleton  from  Guadaloupe. 


Conglomerate  containing  coins. 

with  which  the  history  of  the  world's  life  began.  Fig.  457 
represents  a  coin  conglomerate,  containing  coins  of  silver,  of  the 
reign  of  Edward  I.,  found  at  a  depth  of  ten  feet  below  the  bed 


QUATERNARY   AGE.  —  MAN.  371 

of  the  river  Dove  in  England  ;  and  Fig.  456,  a  portion  of  a 
human  skeleton  firmly  imbedded  in  a  modern  shell-limestone 
of  Guadaloupe,  the  former  owner  of  which  was  two  centuries 
since  a  righting  Carib.  ?)fe^ 

6.  Man  at  the  Head  of  the  System  of  Life.  —  With  the  crea- 
tion of  Man  a  new  era  in  Geological  history  opens.     In  earliest  "T 
time  only  matter  existed,  —  dead  matter.     Then  appeared  life,  , 
-  unconscious  life  in  the  plant,  conscious  and  intelligent  life  in      '^f^' 

the  animal.     Asjes  rolled  by,  with  varied  exhibitions  of  animal'  , 

$&<-  ^\ 
and  vegetable  life.     Finally  Man  appeared,  a  being  made  of 

matter  and  endowed  with  life,  but,  more  than  this,  partaking'^  ' 
of  a  spiritual  nature.     The  systems  of  life  belong  essentially  ' 
to  time  ;  but  Man,  through  his  spirit,  to  the  opening  and  infinite^, 

" 


disobedience  of  any  moral  law,  the  only  one  subject  to  degra-^^    " 
dation  through  excesses  of  appetite  and  violation  of  moral  , 


law,  the  only  one  with  the  will  and  power  to  make  nature's  J 
forces  his  means  of  progress. 

Man  shows  his  exalted  nature  in  his  material  structure. 
His  fore-limbs  are  not  made  for  locomotion,  as  in  all  quad- 
rupeds ;  they  are  removed  from  the  locomotive  to  the  cephalic 
series,  being  fitted  to  serve  the  head,  and  especially  the  intel- 
lect and  soul.  Man  stands  erect,  his  body  placed  wholly 
under  the  brain,  to  which  it  is  subservient;  and  his  feet 
are  simply  for  support  and  locomotion,  and  not,  as  in  the 
Monkeys,  grasping  or  prehensile  organs  for  climbing.  His 
whole  outer  being,  in  these  and  other  ways,  shows  forth  the 
divine  feature  of  the  inner  being. 

3.  Extinction  of  Species  in  Modern  Times. 

Species  are  becoming  extinct  in  the  present  era,  as  they 
have  in  the  past.  Man  is  now  a  prominent  means  of  this 
destruction.  The  Dodo,  a  laiye  bird  looking  like  an  overgrown 
chicken  in  its  plumage  and  wings  (Fig.  458),  was  abundant  in 


372  CENOZOIC  TIME. 

the  island  of  Mauritius  until  early  in  the  commencement  of 
the  eighteenth  century. 

Fig.  458. 


Dodo,  with  the  Solitaire  in  tae  background. 

The  Moa  or  Dinornis  is  a  New  Zealand  bird  of  the  Ostrich 


CENOZOIC   TIME.  373 

kind  that  was  living  less  than  a  century  since ;  it  was  10  or 
12  feet  in  height,  and  the  tibia  ("  drumstick  ")  30  to  32  inches 
long.  In  Madagascar  remains  of  a  still  larger  bird,  but  of 
similar  character,  occur,  called  an  jfflpyomis  ;  its  egg  is  over 
a  foot  (13i  inches)  long.  The  Auk,  a  bird  of  Northern  seas, 
has  become  extinct  within  the  last  25  years ;  the  last  was 
seen  in  1844.  These  are  a  few  of  the  examples  of  the  modern 
extinction  of  species. 

The  progress  of  civilization  tends  to  restrict  forests  and 
forest-life  to  narrower  and  narrower  limits.  The  Buffalo  once 
roamed  over  North  America  to  the  Atlantic,  but  now  lives 
only  on  the  Eocky  Mountain  slopes  west  of  the  Missouri  Eiver. 
The  beaver,  wolf,  bear,  and  wild-boar  were  formerly  common 
in  Britain,  but  are  now  wholly  exterminated. 

GENERAL  OBSERVATIONS  ON  THE  CENOZOIC 

ERA. 

1.  Contrast  between  the  Tertiary  and  Quaternary  ages  in  geo- 
graphical progress.  —  The  review  of  Cenozoic  time  has  brought 
out  the  true  contrast  in  the  results  of  the  Tertiary  and  Qua- 
ternary ages. 

The  Tertiary  carried  forward  the  work  of  rock-making  and 
of  extending  the  limits  of  the  dry  land  southward,  southeast- 
ward, and  southwestward,  which  had  been  in  progress  through 
the  Cretaceous  period,  and,  indeed,  ever  since  Archaean  time. 

The  Quaternary  transferred  the  scene  of  operations  to  the 
broad  surface  of  the  continent,  and  especially  to  its  middle 
and  higher  latitudes. 

Through  the  Tertiary  the  higher  mountains  of  the  globe 
had  been  rising  and  the  continents  extending ;  and  hence  the 
great  rivers  with  their  numerous  tributaries  —  which  are  the 
offspring  of  great  mountains  on  great  continents  —  began  to 
exist  and  to  channel  out  the  mountains  and  make  valleys 
and  crested  heights.  In  the  Glacial  epoch  this  work  went 
forward  with  special  energy.  The  exposed  rocks  yielded 


374  CENOZOIC   TIME. 

before  the  moving  glacier,  and  the  earth  and  bowlders  formed 
were  taken  up  ibr  distribution  over  the  continental  surface. 
Torrents,  fed  by  the  melting  ice,  were  also  at  work,  and  with 
even  greater  abrading  power  than  the  ice.  Thus  the  excava- 
tion of  valleys  and  the  shaping  of  hills  and  mountains  were 
everywhere  in  progress.  In  the  Champlain  period,  the  low 
level  at  which  the  land  lay,  and  the  melting  of  the  ice,  with 
the  dropping  of  its  earth  and  stones,  enabled  the  flooded 
streams  to  fill  the  great  valleys  deep  with  alluvium.  In  the 
Recent  period,  which  followed,  the  upward  movements  of  the 
land  led  to  a  completion  of  the  terracing  of  the  Champlain 
deposits  along  the  sea-shores  and  about  the  lakes  and  rivers, 
and  finished  off  the  action  of  the  rivers  and  vegetation  in 
spreading  fertility  over  the  land. 

Thus,  under  the  rending,  eroding,  and  transporting  power 
of  fresh  water,  frozen  and  unfrozen,  —  eminently  the  great 
Quaternary  agent,  —  in  connection,  probably,  with  high-lati- 
tude oscillations  of  the  earth's  crust,  the  making  of  the  earth 
was  finally  completed. 

2.  Life.  —  In  the  Cenozoic  era,  as  in  the  preceding,  species 
were  disappearing  and  others  took  their  places.  The  Mam- 
mals of  the  early  Eocene  are  different  in  species  from  those 
of  the  later ;  and  these  from  the  Miocene,  the  Miocene  from 
the  Pliocene,  and  the  Quaternary  from  the  Pliocene. 

According  to  the  present  state  of  discovery,  Mammals  com- 
menced in  the  Mesozoic  era,  late  in  the  Triassic  period,  and 
the  Mesozoic  species  were  all  Marsupials.  They  were  tho 
precursor  species,  prophetic  of  that  expansion  of  the  new  type 
which  was  to  take  place  after  the  Age  of  Eeptiles  had  closed 
In  the  early  Eocene,  at  the  opening  of  the  Age  of  Mam- 
mals, appeared  Herbivores  and  Carnivores  of  large  size.  Tho 
Herbivores  were  mostly  Pachyderms,  related  to  the  Tapir, 
Hog,  and  Rhinoceros,  and  distantly  to  the  Stag.  The  true 
Stag  family  among  Ruminants  commenced  in  the  Miocene ; 
the  Elephant  tribe,  in  the  Miocene ;  the  Bovine  or  Ox  family, 
in  the  Pliocene,  or  late  in  the  Tertiary. 


LENGTH  OF  GEOLOGICAL  TIME.  375 


GENERAL  OBSERVATIONS  ON  GEOLOGICAL 
HISTORY. 

1.    Length  of  Geological  Time. 

By  employing  as  data  the  relative  thickness  of  the  forma- 
tions of  the  geological  ages,  estimates  have  been  made  of  the 
time-ratios  of  those  ages,  or  their  relative  lengths  (pages  269, 
324).  These  estimated  time-ratios  for  the  Paleozoic,  Meso- 
zoic,  and  Cenozoic  are  12  :  3  :  1.  But  the  numbers  may 
be  much  altered  when  the  facts  on  which  they  are  based 
are  more  correctly  ascertained.  It  is  quite  certain  that  the 
first  of  the  Paleozoic  ages  —  the  Silurian  —  was,  at  the  least, 
four  times  as  long  as  either  the  Devonian  or  Carboniferous ; 
and  probable  that  Mesozoic  time  was  not  less  than  three 
times  that  of  the  Cenozoic. 

Hence  comes  the  striking  conclusion  that  the  longest  age 
of  the  world  since  life  began  was  the  earliest,  —  when  the 
earth  numbered  in  its  population  only  Radiates,  Mollusks, 
and  Marine  Articulates,  and,  toward  its  close,  Fishes.  And 
the  time  of  the  earth's  beginnings  before  the  introduction  of 
life  must  have  exceeded  in  length  all  subsequent  time. 

The  actual  lengths  of  these  ages  it  is  not  possible  to  deter- 
mine even  approximately.  All  that  Geology  can  claim  to  do 
is  to  prove  the  general  proposition  that  Time  is  long.  If  time 
from  the  commencement  of  the  Silurian  included  48  millions 
of  years,  which  some  geologists  would  pronounce  much  too 
low  an  estimate,  the  Paleozoic  part,  according  to  the  above 
ratio,  would  comprise  36  millions,  the  Mesozoic  9  millions, 
and  the  Cenozoic  3  millions. 

One  of  the  means  of  estimating  the  length  of  past  time  is 
that  afforded  by  the  rate  of  recession  of  the  Falls  of  Niagara. 
The  river  below  the  Falls  flows  northward  in  a  deep  gorge, 
with  high  rocky  walls,  for  seven  miles,  toward  Lake  Ontario. 
It  is  reasonably  assumed  that  the  gorge  has  been  cut  out  by 
the  river,  for  the  river  is  annually  making  progress  of  this 


376  HISTORICAL  GEOLOGY. 

very  kind.  From  certain  fossiliferous  Quaternary  beds  over 
the  country  bordering  the  present  walls,  and  other  evidence, 
it  is  proved  that  the  present  gorge,  about  six  miles  long,  was 
made  after  the  middle  of  the  Champlain  period.  The  pres- 
ent annual  progress  of  the  gorge  from  the  cutting  and  under- 
mining action  of  the  waters  has  been  variously  estimated 
from  three  feet  a  century  to  one  foot  a  year.  At  the  larger 
estimate  of  one  foot  a  year,  the  six  miles  would  have  required 
31,000  years  ;  or  double  this  if  six  inches  a  year,  as  made  by 
one  observer ;  and  if  the  estimate  be  one  inch  a  year,  or  8  J 
feet  a  century,  the  time  becomes  nearly  380,000  years.  The 
calculation  may  be  regarded  as  establishing,  at  least,  the 
proposition  that  Time  is  long,  although  it  affords  no  satis- 
factory numbers.  Other  modes  of  calculation  fully  establish 
this  general  proposition. 

2.  Geographical  Progress  in  North  America 

The  principal  steps  of  progress  in  the  continent  of  North 
America  are  here  recapitulated  :  — 

1.  The  continent  at  the  close  of  the  Archaean  lay  spread 
out  mostly  beneath  the  ocean  (map,  page  19 9).  Although  thus 
submerged,  its  outline  was  nearly  the  same  as  now.     The  dry 
land  lay  mostly  to  the  north,  as  shown  on  the  map.     The 
form  of  the  main  mass  approximated  to  that  of  the  letter  V, 
and  it  had  a  southeast  and  a  southwest  border  nearly  parallel 
to  its  present  outline. 

2.  Through  the  Paleozoic  ages,  as  the  successive  periods 
passed,  the  dry  land   gradually  extended   itself  southward 
owing  to  a  gradual  emergence  :    that  is,  the   sea-border  at 
the  close  of  the  Lower  Silurian  was  probably  as  far  south 
as  the  Mohawk  Valley  in  New  York  ;  at  the  close  of  the  Upper 
Silurian  it  extended  along  not  far  from  the  north  end  of 
Cayuga  Lake  and  Lake  Erie  ;  and  by  the  close  of  the  Devo- 
nian age  the  State  was  a  portion  of  the  dry  land  nearly  to 
its  southern  boundary.     This  progress  southward  of  the  sea- 


GEOGRAPHICAL  PROGRESS.  377 

border  in  New  York  may  be  taken  as  an  example  of  what 
occurred  along  the  borders  of  the  Archaean,  to  the  west- 
ward. In  other  words,  there  was  through  the  Silurian  and 
Devonian  ages  a  gradual  southerly  extension  of  the  dry  part 
of  the  continent,  —  that  is,  to  the  southeastward  and  the 
southwestward. 

By  the  close  of  the  Carboniferous  age,  or  before  the  opening 
of  the  Mesozoic  era,  the  dry  portion  appears  to  have  so  far 
extended  southwardly  as  to  include  nearly  all  the  area  east  of 
the  Mississippi  and  north  of  the  Gulf  States,  along  with  a  part 
of  that  west  of  the  Mississippi,  as  far  nearly  as  the  western 
boundary  of  Kansas. 

3.  Before  the  Silurian  age  began,  and  in  its  first  period, 
great  subsidences  were  in  progress  along  the  Lake  Superior 
region,  when  the  thick  Huronian   and   Potsdam  formations 
were  made.     The  facts  show  that  the  depression  of  the  lake, 
and   probably   that   of  some   of  the  other  great  lakes,  and 
also  that  of  the   river   St.  Lawrence,  began  to  form   either 
during  the  closing  part  of  the  Archaean  age  or  in  the  early 
part  of  the  Silurian  age. 

4.  During  the  Paleozoic  ages,  rock-formations  were  in  pro- 
gress over  large  parts  of  the  submerged  portions  of  the  conti- 
nent up  to  the  sea-borders,  and  some  vast  accumulations  of 
sand  were  made  as  drifts  or  dunes  over  the  flat  shores  and 
reefs.     These   rock-formations  had  in  general  ten  times  the 
thickness  along  the  Appalachian  region  which  they  had  over 
the  interior  of  the  continent ;  and  they  were  mostly  fragmental 
deposits  in  the  former  region,  while  mostly  limestones  in  the 
latter.     Hence  two  important  conclusions  follow  :  — 

First.  The  Appalachian  region  was  through  much  of  the 
time  an  exposed  shore-reef  or  flat  of  great  extent,  parallel  in 
course  with  the  present  sea-border  as  well  as  that  of  the 
ancient  Archsean  area ;  while  the  interior  was  a  shallow  sea 
opening  southward  freely  into  the  Gulf  of  Mexico,  and  only 
during  some  few  of  the  periods  with  the  same  freedom  east- 
ward directly  into  the  Atlantic.  Most  of  the  western  part 


378  HISTORICAL  GEOLOGY. 

of  the  sea  (west  of  Missouri)  appears  to  have  been  too  deep 
for  deposits  between  the  Lower  Silurian  and  Carboniferous 
eras. 

Secondly.  The  Appalachian  region  was  undergoing,  through 
the  Silurian  and  Devonian  ages,  great  changes  of  level,  the 
deposits  having  been  made  in  shallow  waters ;  the  region  was 
slowly  sinking,  not  faster  than  the  rate  of  deposition,  and  the 
amount  of  subsidence  exceeded  by  ten  times  that  in  the  In- 
terior Continental  region. 

5.  Of  this  Appalachian  region,  the  Green  Mountain  por- 
tion was  upturned,  rendered  metamorphic,  and  elevated  above 
the  ocean's  level,  at  the  close  of  the  Lower  Silurian;  and 
at  the  same  time  the  valley  of  Lake  Champlain  and  Hudson 
Eiver  was  formed,  if  not  earlier  begun. 

This  valley  and  the  depressions  of  the  Great  Lakes,  and 
also  those  of  the  lakes  extending  in  a  line  through  British 
America  northwestward  from  Lake  Superior  to  the  Arctic 
regions,  lie  not  far  from  the  borders  of  the  Archaean  continent, 
and,  therefore,  between  the  portion  of  the  continent  that  was 
comparatively  stable  dry  land  from  the  time  of  the  Archaean 
onward,  and  that  portion  which  was  receiving  rock-formations 
and  undergoing  oscillations  of  level.  To  this  they  appear  to 
owe  their  origin. 

6.  As  the  Paleozoic  era  closed,  an  epoch  of  revolution  oc 
curred,  in  which  the  rocks  of  the  Appalachian  region  south  of 
New  York  and  west  of  the  Blue  Eidge  underwent  (1)  extensive? 
flexures  or  foldings ;  (2)  immense  faultings  in  some  parts ;  (3) 
consolidation,  and,  in  some  eastern  portions,  crystallization 
or  metainorphism,  with  the  loss  of  bitumen  by  the  coal-beds 
changing  them  into  anthracite.     These  changes  affected  the 
region  from  New  York  to  Alabama.     The  effects  of  heat  and 
uplift  were  more  decided  toward  the  Atlantic  than  toward  the 
interior,  showing  that  the  force  producing  the  great  results 
was  exerted  in  a  direction  from  the  Atlantic  inland,  or  from 
the  southeast  toward  the  northwest.     The  Alleghany  Moun- 
tains were  then  made ;  and  they  were,  consequently,  in  ex- 
istence when  the  Mesozoic  era  opened. 


GEOGRAPHICAL  PROGRESS.         379 

These  mountains  are  parallel  to  the  eastern  outline  of  the 
original  Archaean  continent. 

Similar  changes  may  have  taken  place  on  the  Pacific  side ; 
but  the  facts  thus  far  observed  are  opposed  to  such  a  con- 
clusion. 

This  epoch  of  revolution  was  a  time  of  mountain-making 
also  in  Europe. 

7.  In  the  early  or  middle  Mesozoic  period  (the  continent 
being  largely  dry  land,  as  stated  in  the  latter  part  of  §  2), 
long  depressions  in  the  surface  of  the  continent,  made  in  the 
course  of  the  Appalachian  revolution  and  situated  between 
the  Appalachians   and  the   sea-border,  were  brackish-water 
estuaries,   or  were   occupied    by   fresh-water    marshes    and 
streams ;  and  Mesozoic  sandstone,  shale,  and  coal-beds  were 
formed  in  them.     The  Connecticut  Valley  region  of  Mesozoic 
rocks  (page  285)  is  one  example.     At  the  same  time  there 
were  formations  in  progress  over  the  Eocky  Mountain  region, 
a  vast  area  from  which  the  sea  was  not  excluded,  or  only  in 
part.     At  the  close  of  the  Jurassic  period,  the  Sierra  Nevada, 
and  some  other  great  ranges  on  the  western  side  of  the  con- 
tinent were  made. 

8.  In  the  later  Mesozoic,  or  the   Cretaceous  period,  the 
continent  had  its  Atlantic  and  Gulf  border  yet  under  water, 
and  Cretaceous  rocks  were  formed  about  them,  and  thus  the 
continent  continued  its  former  course  of  enlargement  south- 
eastward (see  map,  page  320).     The   Western   Interior   sea, 
opening  south  into  the  Gulf  of  Mexico,  just  alluded  to,  still 
existed,  and  deposits  were  made  in  it  over  a  very  large  part 
of  the  great  region  reaching  from  Kansas  on  the  east  to  the 
Colorado  on  the  west  and  north  perhaps  to  the  Arctic  Ocean. 
The  Pacific  border  was  also  receiving  an  extension  like  the 
Atlantic, 

9.  In  the  early  Cenozoic,  or  the  Tertiary  age,  the  extension 
of  the  Atlantic  and  Pacific  borders  was  still  continued.     With 
its  close  the  progress  of  the  continent  in  rock-making  south- 
eastward and   southwestward   was   very  nearly   completed. 


380  HISTORICAL  GEOLOGY. 

After  the  Eocene  era  had  in  part  passed,  at  the  close  of 
the  Lignitic  period,  there  was  the  making  of  the  Wahsatch 
Mountains  and  other  ranges  in  the  Eocky  Mountain  region, 
and  of  Coast  ranges,  west  of  the  Sierra  Nevada  in  California. 

The  Western  Interior  sea  became  greatly  contracted  after 
this  last  mountain-making  epoch  hy  the  progressing  elevation 
of  the  Rocky  Mountain  region,  and  the  Mexican  Gulf  reduced 
greatly  in  size  (map,  page  345).  During  the  middle  of  the 
Eocene  Tertiary,  the  Ohio  and  Mississippi  emptied  into  an 
arm  of  the  Gulf  just  where  they  now  join  their  waters ;  at 
the  close  of  the  Eocene  the  Ohio  had  taken  a  secondary  place 
as  a  tributary  of  the  Mississippi.  The  great  Missouri  River, 
the  real  trunk  of  the  Interior  river-system  rather  than  the 
Mississippi,  began  its  existence  after  the  Cretaceous  period, 
and  reached  its  full  size  only  toward  the  close  of  the  Tertiary, 
when  the  Rocky  Mountains  finally  attained  their  full  height. 

10.  The  elevation  of  the  Rocky  Mountains,  like  that  of  the 
Appalachians,  was  the  raising  of  the  land  along  a  region  par- 
allel with  the  outline  of  the  original  Archaean  dry  land  (see 
map,  page  199).    The  elevation  of  the  Sierra  Nevada  of  Cali- 
fornia was  a  doubling  of  this  same  line  on  the  west ;  while 
the  elevation  of  the  trap  ridges  and  red  sandstone  of  the  early 
Mesozoic  along  the  Atlantic  border  (page  286)  was  a  doubling 
of  the  line  on  the  east ;  finally  the  elevation  of  the  Cretaceous 
with  the  Lignitic  Tertiary  tripled  the  line  of  heights  on  the 
Pacific  side ;  and  the  later  elevation  of  the  Miocene  added  a 
fourth  line  of  heights  to  the  border  of  the  great  Pacific  Ocean. 

11.  The  continent  being  thus  far  completed,  as  the  Qua- 
ternary Age  was  drawing  on,  operations  changed  from  those 
causing   southern   extension  to  those  producing  movements 
of  ice  and  fresh  waters  over  the  land,  especially  in  the  higher 
latitudes ;  and  thereby  valleys,  great  and  small,  were  exca- 
vated over  the  continent ;  earth  and  gravel  were  transported 
and  made  to  cover  deeply  the  rocks  and  spread  the  continent 
with  fertile  plains  and  hills ;  and,  as  the  final  result,  those 
grand  features  and  those  qualities  of  surface  were  educed  that 
were  requisite  to  make  the  sphere  a  fit  residence  for  Man. 


PROGRESS  OF  LIFE.  381 

3.  Progress  of  Life. 

1  Fact  of  progress  of  life,  —  Life  commenced,  among 
plants,  in  Sea-weeds ;  and  it  ended  in  Palms,  Oaks,  Elms,  the 
Orange,  Rose,  etc.  It  commenced  among  animals  in  Lin- 
gulce  (Mollusks  standing  on  a  stem  like  a  plant),  Crinoids, 
Worms,  and  Trilobites,  and  probably  earlier  in  the  simple  sys- 
temless  Protozoans  (page  185) ;  it  ended  in  Man.  Sea-weeds 
were  followed  by  Lycopods,  Ferns,  and  other  Flowerless  plants, 
and  by  Gymnosperms,  the  lowest  of  Flowering  plants ;  these 
finally  by  the  higher  Flowering  species  above  mentioned,  the 
Palms  and  Angiosperms.  Radiates,  Mollusks,  and  Articulates, 
which  appeared  in  the  early  Silurian,  afterwards  had  Fishes 
associated  with  them;  later,  Reptiles;  later,  Birds  and  in- 
ferior Mammals;  later,  higher  Mammals,  as  Beasts  of  prey 
and  Cattle ;  lastly,  Man. 

2.  Progress  from  marine  to  terrestrial  life,  —  The  Silurian 
was  eminently  the  marine  age  of  the  world.  The  plants 
found  fossil  in  the  Silurian  until  near  its  close  are  sea- weeds, 
and  the  animals  all  marine.  The  animals  of  the  Devonian, 
also,  are  largely  marine ;  but  there  is  a  step  taken  in  terres- 
trial life  by  the  expansion  of  the  type  of  land-plants,  and  the 
appearance  of  Insects. 

In  the  Carboniferous  age,  and  through  the  Mesozoic  era, 
the  continents,  or  large  areas  over  them,  underwent  alterna- 
tions between  a  submerged  and  a  dry  land  state,  leading  a  kind 
of  amphibian  existence.  The  Carboniferous  age  had,  besides 
its  aquatic  life,  Insects,  Spiders,  Centipedes,  terrestrial  Mol- 
lusks, Amphibian  and  other  Eeptiles,  and  a  great  profusion 
of  forest-trees  and  other  terrestrial  vegetation.  In  the  Meso- 
zoic, to  Reptiles  were  added  Birds  and  Mammals,  eminently 
terrestrial  kinds  of  life. 

The  Cenozoic  was  distinctively  a  continental  era.  The 
continents  became  mostly  dry  land  after  its  earliest  period ; 
and,  as  the  Age  of  Man  approached,  they  had  their  full  size 
and  their  present  diversities  of  surface'  and  climate.  With 


332  HISTORICAL   GEOLOGY. 

the  increased  variety  of  conditions  fitted  for  terrestrial  life 
there  was,  beyond  question,  a  great  augmentation  in  the 
number  and  variety  of  terrestrial  species.  Birds  and  Insects 
have  probably  their  greatest  numbers  and  variety  of  species 
in  the  present  age.  Marine  species  still  abound,  but  rela- 
tively to  the  terrestrial  they  are  far  less  numerous  and  less 
extensively  distributed  than  in  the  Mesozoic  and  earlier  ages. 

3.  Progress  was  connected  with  a  constant  change  of  species, 
new  species  appearing  as  others  disappeared.  —  No  species  of 
animal  survived  from  the  beginning  of  life  on  the  globe  to 
the  present  time,  nor  even  through  a  single  one  of  the  several 
geological  ages ;  and  but  few  lived  on  from  the  beginning  of 
any  one  of  the  many  periods  to  its  close,  or  from  one  period 
into  another. 

There  were  widespread  exterminations,  closing  some  of 
the  ages,  as  the  Carboniferous  and  the  Eeptilian ;  there  were 
less  general  exterminations,  closing  the  periods  on  each  of  the 
continents;  and  others,  still  less  general,  at  intermediate 
epochs;  and  often  some  disappearances  accompanied  each 
change  in  the  rock-depositions  that  were  in  progress.  For, 
in  passing  from  one  bed  to  another  above,  some  fossils  fail 
that  occur  below;  and  from  the  strata  of  one  epoch  to  an- 
other, still  larger  proportions  disappear ;  and  sometimes  with 
the  transitions  to  rocks  of  another  period  or  age,  very  nearly 
all  the  species  are  different.  The  rocks  of  the  continents, 
that  are  open  to  examination,  were  made  in  Continental  seas 
and  the  borders  of  the  oceans  adjoining;  and  hence  their 
testimony  with  reference  to  exterminations  does  not  extend 
to  the  Oceanic  areas. 

Of  all  genera  of  animals  now  having  living  species,  only 
one,  the  Mplluscan  genus  Distinct,,  had  species  also  in  the 
earliest  Silurian,  unless  the  Lingulelicc,  of  the  Primordial, 
were,  as  formerly  supposed,  true  Lingulct.  Every  other  genus 
of  that  early  time  sooner  or  later  numbered  only  extinct  spe- 
cies. Afterward  in  the  Lower  Silurian,  Nautilus  and  a  few 
others  were  added  to  Di&wna. 


PROGRESS  OF  LIFE.  383 

Such  unbroken  lines  prove  the  oneness  of  plan  or  system 
through  geological  history. 

Nearly  fifteen  hundred  species  of  Trilobites  have  been 
found  fossil  in  the  Paleozoic  rocks,  and  in  later  formations 
none.  Over  1,000  species  of  the  Ammonite  group  occur  in 
the  Mesozoic  rocks,  —  the  last  then,  or  in  the  early  Tertiary, 
disappeared.  500  species  of  the  Nautilus  tribe  have  been  in 
existence  :  now  there  are  but  two  or  three.  Over  1,000  spe- 
cies of  Ganoids  have  been  found  fossil :  the  tribe  is  now 
nearly  extinct.  The  remains  of  2,500  species  of  plants  and 
over  40,000  species  of  animals  have  been  found  in  the  rocks, 
not  one  of  which  is  now  in  existence.  Thus  the  old  has  been 
ever  passing  away.  But  the  number  of  kinds  of  fossils  dis- 
covered cannot  be  the  number  of  species  that  have  existed ; 
and  the  above  numbers  of  marine  species  may  safely  be  mul- 
tiplied by  ten,  and  of  terrestrial  by  a  thousand. 

4.  Progress  not  always  begun  by  the  introduction  of  the  low- 
est species  of  a  group.  —  Mosses,  although  inferior  to  Lycopods 
and  Ferns,  appear  to  have  been  of  later  introduction,  for  no 
remains  have  been  found  in  the  Carboniferous  or  Devonian 
rocks,  although  there  are  relics  of  both  of  the  other  tribes  of 
plants. 

The  earliest  of  Fishes,  instead  of  being  those  of  lowest 
grade,  were  among  the  highest :  they  were  Ganoids,  or  reptil- 
ian Fishes.  Trilobites,  found  in  the  first  fauna  of  the  Silu- 
rian, are  not  the  lowest  of  Crustaceans.  No  fossil  Snakes 
have  been  found  below  the  Cenozoic,  although  large  Eeptiles 
abounded  in  the  Mesozoic.  Oxen  date  from  the  later  Ter- 
tiary, long  after  the  first  appearance  of  many  higher  Mam- 
mals, as  Tigers,  Dogs,  Monkeys,  etc. 

There  was  upward  progress  in  the  grand  series  of  species, 
as  stated  on  page  381 ;  but  there  was  not  progress  in  all  cases 
from  the  lowest  species  to  the  highest. 

5.  The  earliest  species  of  a  group  were  often  those  of  a  compre- 
hensive type.  —  The  Ganoid  fishes  are  an  example  of  these 
comprehensive  types.     As  stated  on  page  238,  they  were  in- 


384  HISTORICAL  GEOLOGY. 

termediate  in  some  respects  between  Fishes  and  Eeptiles; 
they  were  fishes  comprehending  in  their  structure  some  Rep- 
tilian characters,  and  hence  called  comprehensive  types. 

The  earliest  Mammals  were  Marsupials,  or  species  of  Mam- 
mals comprehending  in  their  structure  some  characteristics  of 
oviparous  Vertebrates  (see  page  176),  and,  therefore,  in  certain 
respects  intermediate  between  Mammals  and  Oviparous  Ver- 
tebrates. 

The  vegetation  of  the  coal-era  consisted  largely  of  trees  al- 
lied to  the  Lycopods  or  Ground-pine  of  the  present  day ;  and 
these,  as  well  as  the  Lycopods,  constitute  a  type  intermediate 
in  some  points  between  Ferns  and  Pines  or  Conifers  (page 
233). 

In  the  Mesozoic  the  most  characteristic  plants  wrere  Cy- 
cads;  and  these  comprehended  in  their  structure  something 
of  three  distinct  types.  They  are  closely  like  Conifers  in 
structure  and  fruit ;  but  they  are  like  Ferns  in  the  way  the 
leaves  unfold  and  in  some  other  points,  and  like  Palms  in 
their  foliage  (page  288). 

These  comprehensive  types  embraced  in  their  natures  usu- 
ally the  features  of  some  type  that  was  to  appear  in  the  fu- 
ture. Thus,  the  Ganoid  fishes  of  the  Devonian  foreshadowed 
the  Amphibians,  the  first  fossils  of  which  occur  afterward  in 
the  early  Carboniferous. 

6.  Harmony  in  the  life  of  a  period  or  age,  —  Through  the  ex- 
istence of  these  comprehensive  types,  and  also  in  other  ways, 
there  was  always  a  striking  degree  of  harmony  between  the 
species  making  up  the  population  —  or  the  fauna  and  flora 
—  of  each  period  in  the  world's  history. 

Among  the  plants  of  the  Carboniferous  age  there  were  - 
(I)  the  highest  of  the  Cryptogams,  or  Flowerless  plants,  the 
Ferns ;  (2)  the  lowest  of  Phenogams  (Gymnosperms),  or  Flow- 
ering plants,  species  having  only  inconspicuous  and  imperfect 
flowers,  and  hence  almost  flowerlcss ;  and  (3)  the  intermediate 
types  of  Lycopods  (Lepidodendrids  and  Sigillarids). 

Again,  in  the  Mesozoic  the  terrestrial  Vertebrate  life  in- 


PROGRESS   OF  LIFE.  385 

eluded  —  (1)  Reptiles,  which  are  oviparous  species ;  (2)  Birds, 
also  oviparous  species ;  (3)  reptilian  Birds,  having  long  tails 
like  the  Reptiles,  and  in  part,  at  least,  true  teeth,  —  a  compre- 
hensive type ;  (4)  Reptiles  that  had  the  hollow  leg-bones,  and 
the  biped  locomotion,  of  birds,  with  some  other  bird-like  char- 
acteristics; (5)  semi-oviparous  Mammals,  or  Marsupials,  an 
intermediate  type  between  ordinary  Mammals  and  the  ovip- 
arous Reptiles  and  Birds. 

7.  Causes  of  the  extinction  of  species  and  tribes.  —  1.  Some 
cpecies  of  plants  and  animals  require  dry  land  for  their  sup- 
port and  growth  ;  some,  fresh-water  marshes  or  lakes  ;  some, 
brackish  water ;  some,  sea-shore  or  shallow  marine  waters ; 
some,  deeper  ocean-waters. 

Hence  (a)  movements  in  the  earth's  crust  submerging  large 
Continental  areas,  or  raising  them  from  the  condition  of  a  sea- 
bottom  to  dry  land,  would  exterminate  life  :  sinking  them 
in  the  ocean,  extinguishing  terrestrial  life ;  raising  them  from 
the  ocean,  extinguishing  marine  life.  In  early  times,  when 
the  Continental  surface  was  in  general  nearly  flat,  a  change  of 
level  of  a  few  hundred  feet,  or  perhaps  of  even  100,  would 
have  been  sufficient  for  a  wide  extermination.  If  a  modern 
coral  island  were  to  be  raised  150  feet,  its  reef-forming  corals 
would  all  be  killed ;  or  if  sunk  in  the  ocean  150  feet,  the 
same  result  would  follow,  —  because  the  species  do  not  groAV 
below  a  depth  of  100  feet.  And  if  all  the  coral-reefs  of  the 
Pacific  Were  simultaneously  sunk  or  raised  to  the  extent 
stated,  there  would  be  a  total  extinction  of  a  large  number  of 
species. 

(&)  Along  a  sea-coast,  the  bays  and  inlets  sometimes  are 
closed  by  barriers  thrown  up  by  the  sea,  and  hence  become 
fresh,  killing  all  marine  life.  Again,  barriers  are  often  washed 
away  by  the  sea,  and  then  salt  water  enters,  destroying  fresh- 
water life. 

2.  Species  also  endure  a  limited  range  of  temperatures : 
some  are  confined  thereby  to  the  equatorial  regions  only; 
some,  to  the  cooler  part  of  the  tropical  zone ;  some,  to  the 


386  HISTOKICAL  GEOLOGY. 

warmer  temperate  latitudes  ;  some,  to  the  middle  temperate ; 
some,  to  the  colder  temperate  ;  some,  to  the  frigid  zone  ;  and 
few  species  live  through  two  such  zones.  So  also,  for  the 
same  reason,  they  are  confined  to  specific  ranges  of  height 
above  the  sea-level ;  or  of  depths  below  the  ocean's  surface. 

Hence,  (a)  as  the  earth  has  gradually  cooled  in  its  climates 
from  a  time  of  universal  tropics  to  that  of  the  present  condi- 
tion, the  larger  part  of  those  tribes  or  families  that  were  fitted 
for  the  earlier  condition  of  the  globe  in  the  course  of  time 
became  extinct. 

Again,  (6)  any  temporary  change  of  climate  over  the 
globe  —  from  cold  to  warm  or  warm  to  cold  —  would  have 
exterminated  species.  An  increase  in  the  extent  and  height 
of  Arctic  lands  would  have  increased  the  cold  directly,  be- 
sides shutting  out  from  the  northern  seas  the  warm  cur- 
rents of  the  oceans ;  and  thereby  cold  winds  would  have 
been  sent  south  over  the  continents,  and  cold  oceanic  cur- 
rents south  along  the  borders  of  the  oceans,  or  the  Conti- 
nental seas.  This  cause  is  one  capable  of  carrying  destruc- 
tion over  the  Occident  and  Orient  simultaneously. 

On  the  contrary,  a  diminution  in  the  extent  of  Arctic 
lands,  making  the  higher  regions  open  seas,  and  opening  the 
Arctic  to  the  warm  currents  of  the  oceans,  or  an  increase  in 
the  extent  of  tropical  lands  for  the  sun  to  heat,  would  have 
increased  the  heat  of  the  globe  and  sent  a  warm  climate  far 
north. 

Such  changes  are  destructive  to  living  species.  It  is  sug- 
gested on  page  329  that  the  destruction  of  life  at  the  close 
of  the  Mesozoic  may  have  arisen  from  the  cause  here  ex- 
plained. 

3.  Any  cause  that  in  past  time  led  to  variations  in  species 
tended  to  obliterate  old  characteristics  and  introduce  those 
that  were  new. 

8,  A  parallelism  between  the  progress  in  the  system  of  life  and 
the  development  from  the  embryo  or  young  state  of  a  species.  — 
The  young  gar-pikes  (Ganoids)  of  North  American  waters  have 


PROGRESS   OF  LIFE.  387 

a  vertebrated  tail ;  and  so  it  was  with  the  Gars  of  the  young 
world.  The  young  of  the  higher  Crustaceans,  Shrimps,  Lob- 
sters, and  Crabs,  are  very  similar, —  strangely  similar,  it  might 
be  said  by  one  not  familiar  with  the  generality  of  Nature's 
laws,  —  to  many  Crustaceans  of  the  young  world,  that  is,  of  its 
earliest  age  after  life  began.  Again,  the  young  of  the  higher 
Insects  are  grubs  and  caterpillars ;  and  these  are  related  in 
important  respects  to  Worms,  the  lowest  of  Articulates  and 
the  kind  that  long  preceded  Insects.  This  principle,  announced 
by  Agassiz,  might  be  illustrated  by  examples  from  all  depart- 
ments of  the  animal  kingdom. 

9,  Progress  always  the  gradual  unfolding  of  a  system.  —  Man 
the  culmination  of  that  system.  —  There  were  higher  and  lower 
species  appearing  through  all  the  ages,  but  the  successive  pop- 
ulations were  still,  in  their  general  range,  of  higher  and  higher 
grade  ;  and  thus  the  progress  was  ever  upward.  The  type  or 
plan  of  vegetation,  and  "the  four  grand  types  or  plans  of  ani- 
mal life,  the  Eadiate,  Molluscan,  Articulate,  and  Vertebrate, 
were  each  displayed  under  multitudes  of  tribes  and  species, 
rising  in  rank  with  the  progress  of  time,  and  all  under  rela- 
tions so  harmonious  and  so  systematic  in  their  successions 
that  they  seem  like  the  expression  —  in  material  living 
forms  —  of  one  divine  purpose.  A  scheme  carried  forward 
by  infinite  wisdom  should  exhibit,  through  each  step  of  its 
progress,  that  complete  adaptation  to  external  conditions 
which  pervades  the  actual  system  of  Nature,  and  could  result 
in  no  other  than  this  very  system.  Its  progress,  if  by  divine 
power,  should  be,  as  zoological  history  attests,  a  development, 
an  unfolding,  an  evolution. 

With  every  new  fauna  and  flora  in  the  passing  periods, 
%here  was  a  fuller  and  higher  exhibition  of  the  kingdoms  of 
life.  Had  progress  ceased  with  the  Eeptilian  age,  the  system 
might  have  been  pronounced  the  scheme  of  an  evil  demon. 
But,  as  time  moved  on,  higher  races  were  introduced;  and 
finally  Man  came  forth, —  not  in  strength  of  body,  but  in 
the  majesty  of  his  spirit ;  and  then  living  nature  was  full 


388  HISTORICAL   GEOLOGY. 

of  beneficence.  The  system  of  life,  about  to  disappear  as  a 
thing  of  the  past,  had  its  final  purpose  fulfilled  in  the  crea- 
tion of  a  spiritual  being,  —  one  having  powers  to  search  into 
the  depths  of  nature  and  use  the  wealth  of  the  world  for 
his  physical,  intellectual,  and  moral  advancement,  that  he 
might  thereby  prepare,  under  divine  aid,  for  the  new  life  in 
the  coming  future. 

Thus,  through  the  creation  of  Man  completing  the  system 
of  life,  all  parts  of  that  system  became  mutually  consistent 
and  full  of  meaning,  and  Time  was  made  to  exhibit  its  true 
relation  to  Eternity. 

10.  The  progress  in  the  system  of  life,  a  progress  in  ceph- 
alization.  —  A  frog  in  the  young  state  is  a  tadpole ;  that  is,  has 
a  long  tail  behind,  and  outside  gills  either  side  of  the  head, 
and  it  is  hardly  above  the  lower  fishes  in  grade.  On  passing 
to  the  adult  state,  the  body  is  shortened  in  behind  by  the  loss 
of  the  tail,  the  fish-like  gills  are  dropped  off  from  the  head,  and, 
simultaneously,  the  anterior  or  head  extremity  becomes  vastly 
improved  in  its  structure  and  functions.  This  transfer  of 
forces  anteriorly  marked  in  abbreviation  behind  and  improve- 
ment in  the  rest  of  the  animal,  especially  in  the  organs  of  the 
head,  that  is,  cephalically  (the  Greek  Ke$a\ri  meaning  luad}) 
is  an  example  under  the  principle  of  cephalization.  There  is 
similar  headward  progress  in  all  development  from  the  young 
state,  whatever  the  class  of  animal ;  and  in  Man,  at  the  head 
of  the  system,  many  years  pass  before  the  structure  has  the 
degree  of  cephalization  that  belongs  to  maturity.  In  a  fly, 
the  young,  a  maggot,  is  much  like  a  worm,  the  body  consisting 
of  a  number  of  similar  segments  and  the  head  extremity  little 
superior  to  the  opposite.  But  in  the  adult  fly,  this  extremity 
has  its  well-constructed  head  and  senses,  and  the  posterior  ex- 
tremity, besides  being  reduced  in  relative  size,  aids  no  longer 
in  locomotion ;  the  development  is,  in  a  wonderful  degree,  a 
cephalization  of  the  structure.  Such  examples  of  the  prin- 
ciple of  cephalization  are  afforded  by  every  part  of  the  animal 
kingdom. 


PROGRESS  OF  LIFE.  389 

The  principle  is  exemplified,  also,  in  the  relations  of  the 
inferior  species  of  a  group  to  the  higher.  A  Lobster  and  a 
Crab  (both  Decapod  Crustaceans)  are  essentially  alike  in  fun- 
damental points  of  structure.  The  Lobster  has  a  very  large 
and  powerful  tail  (abdomen),  a  long  and  loosely  compacted 
head,  and  also  large  and  spreading  head-organs ;  while  the 
Crab,  much  the  higher  species,  has  the  tail  reduced  to  a  small, 
feeble  organ,  hid  away  in  a  groove  under  the  thorax,  and,  at 
the  same  time,  the  head  and  the  organs  of  the  senses  and 
mouth  connected  with  it  are  closely  compacted.  Abbrevia- 
tion behind,  and  compacting  and  improvement  in  front,  con- 
nected with  differences  of  grade,  are  here  well  displayed. 

Thus  grade  among  the  species  of  a  group  is  marked  by  dif- 
ferences in  the  degree  of  cephalization  of  the  structure ;  and 
this  is  so  through  all  groups. 

If,  then,  difference  in  grade  among  species  is  manifested 
in  difference  in  cephalization,  and  if  also  the  stages  in  the 
development  of  a  species  mark  progress  in  cephalization,  it  is 
plain  that  the  scheme  of  progress  for  the  animal  kingdom  in- 
volved throughout  progressing  cephalization.  In  geological 
history  there  were  vertebrate-tailed  Ganoids  before  the  non- 
vertebrate-tailed,  tailed  Amphibians  and  Birds  before  the 
tailless,  Worms  before  the  compact  and  highly  cephalized 
Insect,  Shrimps  and  Lobsters  before  Crabs ;  and  so  in  other 
branches  of  the  Animal  Kingdom.  In  Man,  the  last  term  in 
the  series,  cephalization  reached  its  extreme  limit. 

The  system  of  progress  hence  involved  also  changes  in  ani- 
mal structures.  An  animal  with  the  high  senses  of  an  Insect 
could  not  have  the  form  of  a  Worm  ;  or  those  of  a  Crab,  the 
form  of  a  Lobster ;  or  those  of  Man,  the  body  or  head  of  a 
Monkey. 

11.  Were  the  intervals  between  species  or  groups  in  the  suc- 
cession, through  past  time,  abrupt,  or  gradual  ?  —  As  Geology  is 
the  history  of  the  progress  of  the  earth  and  its  life,  the  science 
is  naturally  looked  to  for  a  decision  of  the  great  question, 
Whether,  in  the  succession  of  species  during  past  time,  there 


390  HISTORICAL  GEOLOGY. 

were  gradual  transitions  between  them  or  not.  Its  testimony 
could  not,  however,  be  decisive,  unless  the  record,  in  some 
parts  at  least,  were  a  nearly  unbroken  one. 

There  is  abundant  evidence  that,  to  a  large  extent,  it  is,  as 
has  been  claimed,  a  very  broken  record.  For  example :  there 
is  not,  on  the  eastern  half  of  North  America,  the  Atlantic  bor- 
der included,  a  species  of  the  marine  Molluscan  or  Radiate 
life  of  that  border  during  the  long  Triassic  and  Jurassic  periods. 
That  there  were  abundant  species  in  the  seas  is  evident  from 
the  rocks  of  these  eras  in  Europe.  Coast  deposits  on  the 
Atlantic  must  have  been  made ;  but  they  are  out  of  reach  be- 
neath the  ocean's  waters.  Again,  two  jaw-bones  of  one  species 
of  Marsupial  Mammal  are  all  the  relics  that  have  been  found 
of  these  animals  in  rocks  of  the  North  American  Triassic, 
Jurassic,  and  Cretaceous  periods,  or  the  whole  of  Mesozoic 
time ;  and  yet,  if  there  were  one  species  in  the  Triassic,  and 
two  individuals,  there  were  probably  a  large  number  of  species, 
and  multitudes  must  have  lived  and  died  through  the  Meso- 
zoic era.  In  Europe,  one  single  specimen  of  a  bird  has  been 
found  in  Jurassic  rocks,  out  of  the  myriads  of  individuals  and 
the  great  numbers  of  species  that  must  then  have  lived.  Only 
a  very  few  kinds  of  plants  have  been  found  in  the  Mesozoic 
formations  of  North  America,  and  yet,  the  continent  must 
have  been  buried  in  foliage  through  all  the  successive  periods 
after  the  Carboniferous  age. 

It  has  to  be  admitted  that  we  know  very  little  about  the 
past  terrestrial  life  of  the  globe,  and  also  that  there  are  some 
great  breaks  in  the  succession  of  marine  life.  Moreover, 
breaks,  as  geological  history  shows,  may  exist  where  the  rocks 
follow  one  another  consecutively  without  any  apparent  inter- 
ruption. 

Now,  in  the  succession  of  species  made  known  by  geology, 
the  transitions  connecting  species  or  groups  are  abrupt,  and 
not  gradual.  Some  of  the  links  between  genera  have  been 
partially  filled  out  by  recent  discoveries,  as,  for  instance,  that 
between  the  modern  Horse  and  the  Tapir-like  Mammals  of 


PROGRESS   OF  LIFE.  391 

the  Eocene  (page  341),  and  that  between  the  Elephant  and 
the  Mastodon,  etc. ;  but  still  the  species  and  genera  of  Horses 
stand  apart.  In  the  long  geological  succession  of  groups  there 
are  even  fewer  examples  of  blendings  than  occur  in  existing 
life. 

Yet  it  has  to  be  admitted  that  the  above  facts  with  regard 
to  the  breaks  in  the  series  of  rocks  weaken  greatly  this  evi- 
dence against  gradual  transitions.  And  its  force  is  further 
lessened  by  the  fact  that  geological  exploration  has  not  ex- 
tended to  all  parts  of  the  world,  or  exhausted  discovery  in  the 
portions  that  have  been  investigated.  This  is  especially 
true  of  the  terrestrial  life  of  the  globe ;  but  not  so  strongly 
with  regard  to  the  marine  life,  particularly  the  Paleozoic  part, 
since  the  rocks  of  the  earlier  ages  are  mainly  of  marine  origin, 
and  abound  in  fossils. 

There  are  still  some  breaks  that  are  most  remarkable,  what- 
ever allowance  be  made  for  imperfection  of  records.  (1.)  Tri- 
lobites  and  Brachiopods  come  abruptly  into  geological  history 
with  no  recognizable  traces  of  their  antecedents.  (2.)  Fishes, 
the  first  of  Vertebrates,  appear  in  the  later  Silurian,  with  no 
species  between  them  and  the  Invertebrates  as  their  precursors. 
(3.)  The  leaves  of  Angiosperms  (or  trees  of  modern  tribes  re- 
lated to  the  Willow,  Elm,  Magnolia)  and  also  the  Palms,  are 
found  fossil  in  the  Cretaceous  rocks  of  the  continents,  and  none 
whatever  as  yet  in  the  Jurassic. 

The  Triassic  rocks  have  afforded  bones  of  the  first  Mam- 
mals, —  Marsupial  Mammals ;  but  nothing  with  regard  to  the 
line  of  predecessors  connecting  them  with  inferior  oviparous 
species.  The  Tertiary  rocks  of  all  the  continents  abound,  in 
many  places,  in  remains  of  true  Mammals.  Yet  not  a  trace 
of  one  has  been  found  in  the  Cretaceous  strata;  and  this  is 
true  even  in  the  Rocky  Mountain  region,  where  the  strata  are 
mostly  of  shallow-water  origin,  and  partly  of  fresh-water  for- 
mation. These  last  are  examples,  it  is  true,  from  terrestrial 
species.  But  the  very  long  blank  antecedent  to  the  Marsu- 
pials and  to  the  true  Mammals  may  well  suggest  the  pro- 


392  HISTORICAL  GEOLOGY. 

priety  of  making  further  search  before  assuming  that  in  the 
gradation  upward  there  were  no  greater  interruptions  than  are 
illustrated  by  the  variations  among  existing  Mammals. 

In  the  case  of  Man,  the  abruptness  of  transition  is  still 
more  wonderful.  The  Man-ape,  nearest  in  structure  to  Man, 
has  a  cranium  of  but  34  cubic  inches  in  capacity,  or  half  that 
of  the  lowest  of  existing  Man,  and  no  link  between  has  been 
found.  No  human  remains  that  the  past  fifteen  years  of 
active  search  have  brought  to  light  afford  evidence  of  the  ex- 
istence of  a  race  less  perfectly  erect  than  existing  Man,  or 
nearer  to  the  Man-ape  in  essential  characteristics.  The  Man- 
apes  of  the  present  day,  the  Gorilla,  Chimpanzee,  and  Orang- 
Utan,  are  the  terminations  of  lines  of  succession  that  reached 
up  to  them.  But,  as  to  the  line  supposed  to  end  in  Man,  not 
the  first  link  has  been  found.  Thus  geological  discovery 
leaves  Man  alone  at  the  head  of  the  system  of  life,  far  re- 
moved from  his  nearest  allies  among  the  brute  races. 

12.  Origin  of  Species.  —  Such  is  the  direct  evidence  from 
Geology  as  to  the  transitions  between  species.  The  other 
considerations,  derived  from  Geology,  that  have  been  regarded 
as  bearing  on  the  question  of  the  origin  of  species,  are  — 

1.  That  the  system  of  life  exhibits  so  perfect  harmony, 
and  so  complete  oneness  of  law  in  its  several  lines  and  suc- 
cessions, that  it  may  be  truly  called  a  system  of  development 
or  evolution,  whatever  the  method  by  which  it  was  carried 
forward. 

2.  That  since  the  physical  progress  of  the  globe  was  under 
the  action  of  natural  law,  so  the  same  may  naturally  have 
been  true  of  its  organic  progress. 

3.  That,  as  regards  geological  history,  time  is  long. 

These  arguments  in  themselves  are  an  insufficient  basis  for 
a  settlement  of  the  great  question. 

Science  derives  other  evidences  from  the  study  of  living 
plants  and  animals ;  but  this  is  not  the  place  for  their  presen- 
tation. Still  other  arguments  come  from  a  priori,  abstract,  or 
metaphysical  considerations,  and  these  too  would  be  here  out 
of  place. 


PROGRESS  OF  LIFE.  393 

The  biblical  student  finds,  in  the  first  chapter  of  Genesis, 
positive  statements  with  regard  to  the  creation  of  living  be- 
ings. But  these  statements  are  often  misunderstood ;  for 
they  really  leave  the  question  as  to  the  operation  of  natural 
causes  for  the  most  part  an  open  one,  —  as  asserted  by  Augus- 
tine, among  the  Fathers  of  the  Church,  and  by  some  biblical 
interpreters  of  the  present  day;  for  it  says  that  there  were 
but  four  fiats  for  the  whole ;  or  but  two,  excluding  the  first 
for  the  beginning  of  life,  and  the  last  for  the  creation  of  Man. 
And  it  plainly  implies  that,  after  the  fiats,  that  is,  through 
these  expressions  of  the  Divine  Will,  the  new  developments 
went  forward  successively  to  the  completion  of  the  grand 
system. 

In  view  of  the  whole  subject,  the  following  appear  to  be 
the  conclusions  most  likely  to  be  sustained  by  further  re- 
search. 

1.  The  evolution  of  the  system  of  life  went  forward  through 
the  derivation  of  species  from  species,  according  to  natural 
methods  not  yet  clearly  understood,  and  with  few  occasions 
for  supernatural  intervention. 

2.  The  method  of  evolution  admitted  of  abrupt  transitions 
between  species ;  as  has  been  argued  from  the  abrupt  transi- 
tions that  occur  in  the  development  of  animals  that  undergo 
metamorphosis,  and  the  successive  stages  in  the  growth  of 
many  others. 

3.  External  agencies  or  conditions,  while  capable  of  pro- 
ducing modifications  of  structure,  have  had  no  more  power 
toward  determining  the  directions  of  progress  in  the  evolution, 
than  they  now  have  in  determining  the  course  of  progress  in 
development  from  a  living  germ. 

4.  For  the  development  of  Man,  gifted  with  high  reason 
and  will,  and  thus  made  a  power  above  Nature,  there  was 
required,  as  Wallace  has  urged,  the  special  act  of  a  Being 
above  Nature,  whose  supreme  will  is  not  only  the  source  of 
natural  law,  but  the  working  force  of  Nature  herself, 


394  CONCLUSION. 


CONCLUDING  REMARKS. 

Geology  may  seem  to  be  audacious  in  its  attempts  to  unveil 
the  mysteries  of  creation.  Yet  what  it  reveals  are  only  some 
of  the  methods  by  which  the  Creator  has  performed  his  will ; 
and  many  deeper  mysteries  it  leaves  untouched. 

It  brings  to  view  a  perfect  and  harmonious  system  of  life, 
but  affords  no  explanation  of  the  origin  of  life,  or  of  any  of 
nature's  forces. 

It  accounts  for  the  forms  of  continents ;  but  it  tells  nothing 
as  to  the  source  of  that  arrangement  of  the  wide  and  narrow 
continents  and  wide  and  narrow  oceans  that  was  necessary 
to  the  grand  result. 

It  teaches  that  strata  were  made  in  many  successions  as 
the  continents  lay  balancing  near  the  water's  level,  sometimes 
just  above  the  surface,  sometimes  a  little  below ;  but  it  does 
not  explain  how  it  happened  that  the  amount  of  water  was 
of  exactly  the  right  quantity  to  fill  the  great  basin,  and  admit 
of  oscillations  of  the  land  beneath  or  above  its  surface  by  only 
small  changes  of  level ;  for  if  the  water  had  been  a  few  hun- 
dred feet  below  the  level  it  now  has,  the  continents  would 
have  remained  mostly  without  their  marine  strata,  and  the 
plan  of  progress  would  have  proved  a  failure ;  or  if  as  much 
above  its  present  level,  the  land  through  the  earlier  ages  would 
have  been  sunk  to  depths  comparatively  lifeless,  with  no  less 
fatal  results  both  to  the  series  of  rocks  and  the  system  of 


CONCLUSION.  395 

marine  and  terrestrial  life ;  and  in  the  end  there  would  have 
been  broad  and  narrow  strips  of  dry  land  and  archipelagoes, 
in  place  of  the  expanded  Orient  and  Occident. 

It  may  be  said  to  have  searched  out  the  mode  of  develop- 
ment of  a  world.  Yet  it  can  point  to  no  physical  cause  of 
that  prophecy  of  Man  which  runs  through  the  whole  history ; 
which  was  uttered  by  the  winds  and  waves  at  their  work  over 
the  sands,  by  the  rocks  in  each  movement  of  the  earth's  crust, 
and  by  every  living  thing  in  the  long  succession,  until  Man 
appeared  to  make  the  mysterious  announcements  intelligible. 
For  the  body  of  Man  was  not  made  more  completely  for  the 
service  of  the  soul,  than  the  earth,  in  all  its  arrangements 
from  beginning  to  end,  for  the  spiritual  being  that  was  to 
occupy  it.  In  Man,  the  bones  are  not  merely  the  jointed 
framework  of  an  animal,  but  a  framework  shaped  throughout 
with  reference  to  that  erect  structure  which  befits  and  can 
best  serve  Man's  spiritual  nature.  The  feet  are  not  the 
clasping  and  climbing  feet  of  a  monkey ;  they  are  so  made  as 
to  give  firmness  to  the  tread  and  dignity  to  the  bearing  of  the 
being  made  in  God's  image.  The  hands  have  that  fashioning 
of  the  palm,  fingers,  and  thumb,  and  that  delicacy  of  the 
sense  of  touch,  which  adapt  them  not  only  to  feed  the  mouth, 
but  to  contribute  to  the  wants  of  the  soul  and  obey  its 
promptings.  The  arms  are  not  for  strength  alone,  —  for  they 
are  weaker  than  in  many  a  brute,  —  but  to  give  the  greater 
power  and  expression  to  the  thoughts  that  issue  from  within. 
The  face,  with  its  expressive  features,  is  formed  so  as  to  re- 
spond not  solely  to  the  emotions  of  pleasure  and  pain,  but  to 
shades  of  sentiment  and  interacting  sympathies  the  most 
varied,  high  as  heaven  and  low  as  earth,  —  ay,  lower,  in  de- 
based human  nature.  And  the  whole  being,  body,  limbs,  and 
head,  with  eyes  looking,  not  toward  the  earth,  but  beyond  an 
infinite  horizon,  is  a  majestic  expression  of  the  divine  feature 
in  Man,  and  of  the  infinitude  of  his  aspirations. 

So  with  the  earth,  Man's  world-body.  Its  rocks  were  so 
arranged,  in  their  formation,  that  they  should  best  serve  Man's 


396  CONCLUSION. 

purposes.  The  strata  were  subjected  to  metamorphism,  and 
so  crystallized  that  he  might  be  provided  with  the  most  per- 
fect material  for  his  art,  —  his  statues,  temples,  and  dwellings ; 
at  the  same  time  they  were  filled  with  veins,  in  order  to  supply 
him  with  gold  and  silver  and  other  treasures.  The  rocks  were 
also  made  to  enclose  abundant  beds  of  coal  and  iron  ore,  that 
Man  might  have  fuel  for  his  hearths  and  iron  for  his  utensils 
and  machinery.  Mountains  were  raised  to  temper  hot  climates, 
to  diversify  the  earth's  productiveness,  and,  pre-eminently,  to 
gather  the  clouds  into  river-channels,  thence  to  moisten  the 
fields  for  agriculture,  afford  facilities  for  travel,  and  supply 
the  world  with  springs  and  fountains. 

The  continents  were  clustered  mostly  in  one  hemisphere 
to  bring  the  nations  into  closer  union ;  and  the  two  having 
climates  and  resources  the  best  for  human  progress,  —  the 
northern  Orient  and  Occident,  —  were  separated  by  a  narrow 
ocean,  that  the  great  mountains  might  be  on  the  remoter  bor- 
ders of  each,  and  all  the  declivities,  plains,  and  rivers  be  turned 
toward  one  common  channel  of  intercourse.  So,  also,  the 
species  of  life,  both  of  plants  and  animals,  were  appointed 
to  administer  to  Man's  necessities,  moral  as  well  as  physical. 

Besides  these  beneficent  provisions,  the  forces  and  laws  of 
nature  were  particularly  adapted  to  Man,  and  Man  to  those 
laws,  so  that  he  should  be  able  to  take  the  oceans,  rivers,  and 
winds  into  his  service,  and  even  the  more  subtle  agencies, 
heat,  light,  and  electricity ;  and  the  adjustments  were  made 
with  such  precision  that  the  face  of  the  earth  is  actually 
fitted  hardly  less  than  his  own  to  respond  to  his  inner  being : 
the  mountains  to  his  sense  of  the  sublime,  the  landscape,  with 
its  slopes,  its  trees,  its  flowers,  to  his  love  of  the  beautiful,  and 
the  thousands  of  living  species,  in  their  diversity,  to  his  various 
emotions  and  sentiments.  The  whole  world,  indeed,  seems 
to  have  been  made  almost  a  material  manifestation,  in  multi- 
tudinous forms,  of  the  elements  of  his  own  spiritual  nature, 
that  it  might  thereby  give  wings  to  the  soul  in  its  heavenward 
aspirings.  It  may  therefore  be  said  with  truth  that  Man's 


CONCLUSION.  307 

spirit  was  considered  in  the  ordering  of  the  earth's  structure 
as  well  as  in  that  of  his  own  body. 

It  is  hence  obvious  that  the  earth's  history,  which  it  is  the 
object  of  Geology  to  teach,  is  the  true  introduction  to  human 
history. 

It  is  also  certain  that  science,  whatever  it  may  accomplish 
in  the  discovery  of  causes  or  methods  of  progress,  can  take  no 
steps  toward  setting  aside  a  Creator.  Far  from  such  a  result, 
it  clearly  proves  that  there  has  been  not  only  an  omnipotent 
hand  to  create,  and  to  sustain  physical  forces  in  action,  but 
an  all-wise  and  beneficent  Spirit  to  shape  all  events  toward  a 
spiritual  end. 

Man  may  well  feel  exalted  to  find  that  he  was  the  final 
purpose  when  the  word  went  forth  in  the  beginning,  LET 
LIGHT  BE.  And  he  may  thence  derive  direct  personal  assur- 
ance that  all  this  magnificent  preparation  is  yet  to  have  a 
higher  fulfilment  in  a  future  of  spiritual  life.  This  assurance 
from  nature  may  seem  feeble.  Yet  it  is  at  least  sufficient  to 
strengthen  faith  in  that  Book  of  books  in  which  the  promise 
of  that  life  and  "  the  way  "  are  plainly  set  forth. 


APPENDIX. 


A.  — Map  of  the  Vicinity  of  Naples. 

THE  accompanying  map  serves  to  illustrate  the  sketch  on 
page  130.  It  covers  in  breadth  just  20  miles.  It  shows  the 
position  of  Vesuvius ;  its  cone  and  crater ;  the  cinder-cone 
within  the  crater ;  and  the  outer  margin  (called  Sonima,  on 


the  north)  of  a  larger  cone  and  crater,  —  probably  that  of 
A.D.  79,  previous  to  the  eruption  which  destroyed  Pompeii. 
The  crater,  after  some  of  its  eruptions,  has  been  2000  feet 
deep ;  at  other  times  it  has  within  a  solid  lava-plain  near  its 
top,  and  a  cinder-cone  at  centre,  which  was  the  case  at  the 
time  of  the  author's  visit  in  June,  1834.  To  the  southeast 
of  Vesuvius  lies  Pompeii,  tufa-covered;  and  west  of  it,  on 
the  coast,  Herculaneum,  beneath  tufa  of  the  year  79,  the 
lavas  of  six  subsequent  eruptions  separated  by  thin  layers  of 
soil,  and  the  cities  of  Eesina  and  Portici.  West  of  Naples, 


APPENDIX.  399 

Lake  d'Agnano  occupies  the  crater  of  a  volcano ;  the  Solfa- 
tara,  an  area  now  of  steaming  fissures,  with  sulphurous  and 
other  vapors,  another;  and  Astroni  is  a  volcanic  cone  made 
of  tufa.  Pozzuoli,  with  the  Temple  of  Serapis,  whose  few 
standing  columns  bear  evidence  of  great  changes  of  level  in 
the  land,  occupies  a  point  just  west  of  the  limits  of  the 
map;  and  north  of  it  are  the  volcanic  cones  of  Monte  Nuovo 
(thrown  up  in  1538)  and  Monte  Barbaro,  of  unknown  date. 


B.  —  Catalogue  of  American  Localities  of  Fossils. 

THE  following  catalogue  of  American  localities  of  fossils  contains 
only  some  of  the  more  important,  and  is  intended  for  the  conven- 
ience especially  of  the  student-collector. 

Localities  of  Fossils. 

Acadian  Group.  —  Coldbrook,  Ratcliffe's  Millstream,  St.  John,  New 
Brunswick.  —  Long  Arm  of  Canada  Bay,  Newfoundland. 

Potsdam  Group.  —  Swanton,  Vt.  —  Braintree,  Mass.  —  Keeseville  (at 
"High  Bridge"),  Alexandria,  Troy,  N.  Y.  —  Chiques  Ridge,  Pa.  —Falls  of 
St.  Croix,  Osceola  Mills,  Trempaleau,  Wisconsin.  —  Lansing,  Iowa.  —  St. 
Ann's,  Isle  Perrot,  C.  W.  — Near  Beauharnois  on  Lake  St.  Louis,  C.  E. 

Calciferous.  —  Mingan  Islands,  St.  Timothy,  and  near  Beauharnois, 
C.  E.  —  Grand  Trunk  Railway  between  Brockville  and  Prescott,  St.  Ann's, 
Isle  Perrot,  C.  W.  —  Amsterdam,  Fort  Plain,  Canajoharie,  Chazy,  Lafarge- 
ville,  Ogdensburg,  N.  Y. 

Quebec  Group.  —  Mingan  Islands,  Point  Levi,  Philipsburg,  and  near 
Beauharnois,  C.  E.  —  Point  Rich,  Cow  Head,  Newfoundland.  —  Cuts  in  Black 
Oak  Ridge  and  Copper  Ridge,  Knoxville  and  Ohio  Railroad,  Tenn.  —  Malade 
City,  Idaho. 

Chazy  Limestone.  — Chazy,  Gal  way,  "Westport,  N.  Y.  —  One  to  three 
miles  north  of  "the  Mountain"  Island  of  Montreal,  C.  E. — St.  Joseph's 
Island,  Sault  Ste.  Marie,  C.  W.  —  Knoxville,  Lenoir's,  Bull's  Gap,  Kings- 
port,  Tenn. 

Bird's-eye  Limestone.  —  Amsterdam,  Little  Falls,  Fort  Plain,  Adams, 
Watertown,  N.  Y. 

Black  River  Limestone.  —  Watertown,  N.  Y.  —  Ottawa,  C.  W.  — 
Island  of  Montreal,  and  near  Quebec,  C.  E. 

Trenton  Limestone.  —  Adams,  Watertown,  Boonville,  Turin,  Jackson- 
burg,  Little  Falls,  Lowville,  Middleville,  Fort  Plain,  Trenton  Falls,  N.  Y.  — 
Pine  Grove,  Aaronsburg,  Potter's  Fort,  Milligan's  Cove,  Pa.  —  Highgate 


400  APPENDIX. 

Springs,  Vt.  —  Montmorency  Falls  and  Beauport  Quarries  near  Quebec, 
Island  of  Montreal  (quarries  north  of  the  city),  C.  E.  —  Ottawa,  Belleville, 
Trenton  (G.  T.  R.  R.,  west  of  Kingston),  C.  W.  —  Copper  Bay,  Mich.  —  El- 
kader  Mills,  Turkey  River,  Dubuque,  Iowa.  —  Falls  of  St.  Anthony,  St. 
Paul,  Mineral  Point,  Cassville,  Beloit,  Quimby's  Mills  near  Benton,  Wis.  — 
Warren,  Rockton,  Winslow,  Dixon,  Freeport,  Cedarville,  Savanna,  Rockford, 
111.  —  Murfreesborough,  Columbia,  Lebanon,  Tenn. 

Utica  Slate.  —  Turin,  Martinsburg,  Lorraine,  Worth,  Utica,  Cold  Spring, 
Oxtimgo  and  Osquago  Creeks  near  Fort  Plain,  Mohawk,  Rouse's  Point,  N.  Y. 

—  Rideau  River  along  railroad  at  Ottawa,  bed  of  river  two  miles  above,  C.  W. 
Cincinnati   Group.  —  Pulaski,    Rome,    Lorraine,    Boonville,    N.    Y.  — 

Penn's  Valley,  Milligan's  Cove,  Pa.  —  Oxford,  Cincinnati,  Lebanon,  0.  — 
Madison,  Richmond,  Ind.  —  Anticosti,  opposite  Three  Rivers,  C.  E.  — 
Weston  on  the  Humber  River,  nine  miles  west  of  Toronto,  C.  W.  —  Little 
Makoqueta  River,  Iowa.  —  Savannah,  Green  Bay,  "Wis.  —  Thebes,  Alexander 
County  ;  Savanna,  Carroll  County  ;  Scales's  Mound,  Jo  Daviess  County  ; 
Oswego,  Yorkville,  Kendall  County  ;  Naperville,  Dupage  County  ;  Wilming- 
ton, Will  County,  111.  —  Cape  Girardeau,  Mo.  —  Drummond's  Island,  Mich. 

—  Nashville,  Columbia,  Knoxville,  Tenn. 

Medina  Sandstone.  —  Lockport,  Lewiston,  Medina,  Rochester,  N.  Y.  — 
Long  Narrows  below  Lewistown,  Pa.  —  Dun  das,  C.  W. 

Clinton  Group.  —  Lewiston,  Lockport,  Reynolds  Basin,  Brockport,  Roch- 
ester, Wolcott,  New  Hartford,  N.  Y.  —  Thorold  on  Welland  Canal,  Hamilton, 
Ancaster,  Dundas,  C.  W.  —  Hanover,  Ind. 

Niagara.  —  Lewiston,  Lockport,  Gosport,  Rochester,  Wolcott,  N.  Y.  — 
ThoroM,  Hamilton,  Ancaster,  C.  W.  —  Anticosti,  C.  E.  —  Arisaig,  Nova 
Scotia.  —  Racine,  Waukesha,  Wis.  —  Sterling,  Graf  ton,  Savanna,  Chicago, 
Joliet,  111.  —  Marblehead  on  Drummond's  Island,  Michigan.  —  Springfield, 
Cedarville,  Ohio.  —  Delphi,  Waldron,  Jeffersonville,  Madison,  Logansport, 
Peru,  Ind.  —  Louisville,  Ky.  —  The  "  glades  "  of  West  Tennessee.  (Coral- 
line Limestone.  —  Schoharie,  N.  Y.) 

Onondaga  Salt  Group.  —  Buffalo,  Williamsville,  Waterville,  Jerusalem 
Hill  (Herkimer  County),  N.  Y.  —  Gait,  Guelph  (G.  T.  R,  R.),  C.  W. 

Lower  Helderberg  Limestones.  —  Dry  Hill,  Jerusalem  Hill  (Herki- 
mer County),  Sharon,  East  Cobleskill,  Judd's  Falls,  Cherry  Valley,  Carlisle, 
Schoharie,  Clarksville,  Athens,  N.  Y.  —  Pembroke,  Parlin  Pond,  Me.  — 
Gaspe,  C.  E.  —  Arisaig,  East  River,  Nova  Scotia.  —  Peach  Point,  opposite 
Gibraltar,  Ohio.  —  Thebes,  Devil's  Backbone,  111.  —  Bailey's  Landing,  Mo.  — 
"  Glades  "  of  Wayne  and  Hardin  Counties,  Tenn. 

Oriskany  Sandstone.  —  Oriskany,  Vienna,  Carlisle,  Schoharie,  Pucker 
Street,  Catskill  Mountains,  N.  Y.  —  Cumberland,  Md.  —  Moorestown  and 
Frankstown,  Pa.  —  Bald  Bluffs,  Jackson  County,  111.  —  Four  miles  S.  W. 
of  St.  Mary's,  Ste.  Genevieve  County,  Mo. 

Cauda-galli  Grit.  —  Schoharie  (Fucoides  Cauda-galli),  N.  Y. 

Schoharie  Grit.  -  Schoharie,  Cherry  Valley,  N.  Y. 

Upper  Helderberg  Limestones.  —  Black  Rock,  Buffalo,  Williamsville, 


APPENDIX.  401 

Lancaster,  Clarence  Hollow,  Stafford,  Le  Roy,  Caledonia,  Mendon,  Auburn, 
Onondaga,  Cassville,  Babcock's  Hill,  Schoharie,  Cherry  Valley,  Clarksville, 
N.  Y.  —  Port  Colborne,  and  near  Cayuga,  C.  W.  —  Columbus,  Delaware, 
White  Sulphur  Springs,  Sandusky,  Ohio.  —  Mackinac,  Little  Traverse  Bay, 
Dundee,  Monguagon,  Mich.  —  North  Vernon,  Charlestown,  Kent,  Hanover, 
Jeffersonville,  Ind.  —  Louisville,  Ky. 

Marcellus  Shales.  —  Lake  Erie  shore,  ten  miles  S.  of  Buffalo,  Lancaster, 
Alden,  Avon,  Leroy,  Marcellus,  Manlius,  Cherry  Valley,  N.  Y. 

Hamilton  Group.  —  Lake  Erie  shore,  Eighteen  Mile  Creek,  Hamburg, 
Alden,  Darien,  York,  Moscow,  East  Bethany,  Bloomfield,  Bristol,  Seneca 
Lake,  Cayuga  Lake,  Skaneateles  Lake,  Moravia,  Pompey,  Cazenovia,  Delphi, 
Bridgewater,  Richland,  Cherry  Valley,  Seward,  Westford,  Milford,  Portland- 
ville,  N.  Y.  —  Widder  Station  (G.  T.  R.  R.),  near  Port  Sarnia,  C.  W.  —  New 
Buffalo,  Independence,  Rockford,  Iowa.  — Devil's  Bake  Ovan,  Jackson 
County,  Moline,  Rock '  Island,  111.  —  Grand  Tower,  Mo.  —  Thunder  Bay, 
Little  Traverse  Bay,  Mich.  —  Jeffersonville,  Ind.  —  Nictaux,  Bear  River, 
Moose  River,  Nova  Scotia. 

Genesee  Shale.  —  Banks  of  Seneca  and  Cayuga  Lakes,  Lodi  Falls,  Mount 
Morris,  two  miles  south  of  Big  Stream  Point,  Yates  County,  N.  Y.  — 
(Genesee  or  Portage.  —  Delaware,  Ohio.  —  Rockford,  North  Vernon,  Ind. 

—  Danville,  Ky.) 

Portage  Group.  —  Eighteen  Mile  Creek  on  Lake  Erie,  Chautauqua  Lake, 
Genesee  River  at  Portage,  Flint  Creek,  Cashaqua  Creek,  Nunda,  Seneca  and 
Cayuga  Lakes,  N.  Y. 

Chemung  Group.  —  Rockville,  Philipsburg,  Jasper,  Greene,  Chemung 
Narrows,  Troopsville,  Elmira,  Ithaca,  Waverly,  Hector,  Enfield,  Franklin, 
X.  Y.  —  Gaspe,  C.  E. 

Catskill  Group.  — -  Fossils  rare.  —  Richmond's  quarry  above  Mount  Up- 
ton on  the  Unadilla,  Oneonta,  Oxford,  Steuben  County,  south  of  the  Canis- 
teo,  N.  Y. 

Subcarboniferous.  —  Burlington,  Keokuk,  Columbus,  Iowa.  —  Quincy, 
Warsaw,  Alton,  Kaskaskia,  Chester,  111.  —  Crawfordsville,  Greencastle, 
Bloomington,  Spergen  Hill,  New  Providence,  Ind.  —  Hannibal,  St.  Genevieve, 
St.  Louis,  Mo.  —  WTillow  Creek,  Battle  Creek,  Marshal,  Moscow,  Jonesville, 
Holland,  Grand  Rapids,  Mich.  —  Mauch  Chunk,  Pa.  —  Newtonville,  Ohio.  — 
Ice's  Ferry,  on  Cheat  River,  Monongalia  County,  W.  Va.  —  Red  Sulphur 
Springs,  Pittsburg  Landing,  White's  Creek  Springs,  Waynesville,  Cowan, 
Tenn.  — Big  Bear  and  Little  Bear  Creeks,  Big  Crippled  Deer  Creek,  Miss.  — 
Clarksville,  Huntsville,  Ala.  —  Windsor,  Horton,  Nova  Scotia. 

Carboniferous.  —  South  Joggins,  Pictou,  Sydney,  Nova  Scotia.  —  Wilkes- 
barre,  Shamokin,  Tamaqua,  Pottsville,  Minersville,  Tremont,  Greensburg, 
Carbondale,  Port  Carbon,  Lehigh,  Trevorton,  Johnstown,  Pittsburg,  Pa.  — 
Pomeroy,  Marietta,  Zanesville,  Cuyahoga  Falls,  Athens,  Yellow  Creek,  Ohio. 

—  Charlestown,  Clarksburg,  Kanawha,  Salines,   Wheeling,  W.  Va.  —  Saline 
Company's   Mines,    Gallatin  County  ;    Carlinville,    Hodges  Creek,   Macoupin 
County  ;  Colchester,  McDonough  County  ;  Duquoin,    Perry  County  ;  Mur- 

26 


402  APPENDIX. 

physborough,  Jackson  County  ;  Lasalle  ;  Morris,  Mazon,  and  Waupecan  Creeks, 
Grundy  County  ;  Danville,  Pettys'  Ford,  Vermilion  County  ;  Paris,  Edgar 
County  ;  Springfield,  111.  —  Perrysville,  Eugene,  Newport,  Horseshoe  of  Little 
Vermillion,  Veraiilliori  County  ;  Durkee's  Ferry,  near  Terre  Haute,  Vigo 
County  ;  Lodi,  Parke  County  ;  Merom,  Sullivan  County,  Ind.  —  Bell's,  Casey's, 
and  Union  Mines,  Crittenden  County  ;  Hawesville  and  Lewisport,  Hancock 
County  ;  Breckenridge,  Giger's  Hill,  Mulford's  Mines,  and  Thompson's  Mine, 
Union  County  ;  Providence  and  Madisonville,  Hopkin's  County  ;  Bonhar- 
bour,  Daviess  County,  Ky.  —  Muscatine,  Alpine  Dam,  Iowa.  —  Leavenworth, 
Indian  Creek,  Grasshopper  Creek,  Juniata,  Manhattan,  Kansas.  —  Rockwood, 
Emory  Mines,  Coal  Creek,  Careyville,  Tenn.  —  Tuscaloosa,  Ala. 

Triassic.  —  Southbury,  Middlefield,  Portland,  Conn.  —  Turner's  Falls, 
Sunderland,  Mass.  —  Phoenixville,  Pa.  —  Richmond,  Va.  —  Deep  River  and 
Dan  River  Coal-fields,  N.  C. 

Cretaceous.  —  Upper  Freehold,  Middletown,  Marlborough,  Blue  Ball, 
Monmouth  County  ;  Pemberton,  Vincenton,  Burlington  County  ;  Black- 
woodtown,  Camden  County  ;  Mullica  Hill,  Gloucester  County  ;  Woods- 
town,  Mannington,  Salem  County  ;  New  Egypt,  Ocean  County,  N.  J. 
—  Warren's  Mill,  Itawamba  County  ;  Tishomingo  Creek,  R.  R.  cuts,  Hare's 
Mill,  Carrollsville,  Tishomingo  County  ;  Plymouth  Bluff,  Lowndes  County  ; 
Chawalla  Station  (M.  &  C.  R.  R.),  Ripley,  Tippah  County  ;  Noxubee,  Macon, 
Noxubee  County  ;  Kemper,  Pontotoc  and  Chickasaw  Counties,  Miss.  — 
Finch's  Ferry,  Prairie  Bluff,  on  Alabama  River  ;  Choctaw  Bluff,  on  Black 
Warrior  River  ;  Greene,  Marengo,  and  Lowndes  Counties,  Ala.  —  Fox  Hills, 
Sage  Creek,  Long  Lake,  Great  Bend,  Cheyenne  River,  etc.,  Nebraska.  — 
Fort  Barker,  Fort  Hayes,  Fort  Wallace,  Kansas.  —  Fort  Lyon,  Santa  Fe, 
New  Mexico. 

Eocene.  —  Everywhere  in  Tippah  County  ;  Yockeney  River  ;  New  Pros- 
pect P.  0.,  Winston  County  ;  Marion,  Lauderdale  County  ;  Enterprise, 
)larke  County  ;  Jackson,  Satartia,  Yazoo  County ;  Homewood,  Scott  County  ; 
£hickasawhay  River,  Clarke  County  ;  Winchester,  Red  Bluff  Station,  Wayne 
Bounty ;  Vicksburg,  Amsterdam,  Brownsville,  Warren  County  ;  Brandon, 
Byram  Station,  Rankin  County  ;  Paulding,  Jasper  County,  Miss.  —  Clai- 
oorne,  Monroe  County  ;  St.  Stephen's,  Washington  County,  Ala.  —  Charles- 
ton, S.  C.  —  Tampa  Bay,  Florida.  —  Fort  Washington,  Fort  Marlborough, 
Piscataway,  Md. — Maiibourne,  Va. — Brandon,  Vt.  —  In  New  Jersey,  at 
Farmingdale,  Squankum  and  Shark  River,  Monmouth  Co.  —  Green  River, 
Fort  Bridger,  Wyoming.  —  Canada  de  las  Uvas,  Cal. 

Miocene.  —  Gay  Head,  Martha's  Vineyard,  Mass.  —  Shiloh,  Jericho, 
Cumberland  County,  and  Deal,  Monmouth  County,  N.  J.  —  St.  Mary's,  Eas- 
ton,  Md.  —  Yorktown,  Suffolk,  Smithfield,  Richmond,  Petersburg,  Va.  — 
Astoria,  Willamette  Valley,  John  Day  Valley,  Oregon.  —  San  Pablo  Bay, 
Ocoya  Creek,  San  Diego,  Monterey,  San  Joaquin  and  Tulare  Valleys,  Cal.  — 
White  River,  Upper  Missouri  Region.  —  Crow  Creek,  Colorado. 

Pliocene.  —  Ashley  and  Santee  Rivers,  S.  C.  —  Platte  and  Niobrara 
Rivers,  Upper  Missouri.  —  John  Day  Valley,  Oregon.  —  Sinker  Creek, 
Idaho.  —  Alameda  County,  Cal. 


APPENDIX.  403 


C.  —  Geological  Implements,  Specimens,  etc. 

1.  Implements.  —  The  student  requires  for  his  geological  excur- 
sions and  research  the  following  implements  :  — 

(1.)  A  hammer.     If  his  object  is  to  get  specimens  of  hard  rocks,  or  obtain 
minerals  from  such  rocks,  it  should  have  the  form  in  Fig.  459,  the  edge  being 
in  the  direction  of  the  handle.     But  if  fossils  are  to  be  collected, 
this  edge  should  be  transverse  to  the  handle.     The  face  should 
be  flat,  and  nearly  square,  with  its  edges  sharp  instead  of  rounded. 
The  socket  for  the  handle  should  be  large,  that  the  handle  may 
be  strong.     The  hammer,  for  ordinary  excursions,  should  weigh 
1£  pounds  exclusive  of  the  handle  ;  the  handle  should  be  about 
12  inches  long.     Another  is  required  for  trimming  specimens, 
weighing  half  a  pound. 

(2. )  A  steel  ch'iscl,  6  inches  long,  such  as  is  used  by  stone- 
cutters.    Also,  another  half  this  size. 

(3.)  A  clinometer,  with  magnetic  needle  attached.     The  best 
kind  is  a  clinometer-compass  3  inches  in  diameter,  having  a 
square  base  about  3|  inches  each  side,  two  sides  of  the  base  being  parallel  to  the 
north  and  south  line  of  the  compass. 

(4.)  A  small  magnet.  A  magnetized  blade  of  a  pocket-knife  is  a  good 
substitute. 

(5.)  A  measuring-tape  50  feet  long.  The  field  geologist  should  know  ac- 
curately the  measurements  of  his  own  body,  his  height,  length  of  limbs,  step 
or  pace,  that  he  may  use  himself,  whenever  needed,  as  a  measuring-rod. 

(6. )  In  many  cases,  a  pick,  a  crow-bar,  a  sledge-hammer  of  4  to  8  pounds' 
weight,  and  the  means  of  blasting,  are  necessary. 

(7.)  Besides  the  above,  a  barometer  and  surveyor's  instruments  are  occa- 
sionally required.  Of  the  latter,  a  hand-level  is  a  desirable  instrument  for 
determining  small  elevations  by  levelling  ;  it  is  a  simple  brass  tube,  with 
cross-hairs,  bubble,  and  mirror.  A  first-rate  aneroid  barometer  is  excellent 
for  all  heights  between  5  feet  and  2,000  feet  ;  and,  having  one,  the  hand- 
level  is  superfluous. 

2.  Specimens.  —  Specimens  for  illustrating  the  kinds  of  rocks 
should  be  carefully  trimmed  by  chipping  to  a  uniform  size,  pre- 
viously determined  upon  :  3  inches  by  4  across,  and  1  inch  through, 
is  the  size  commonly  adopted.     In  the  best  collections  of  rocks,  the 
angles  are  squared  and  the  edges  made  straight  with  great  precision. 
They  should  have  a  fresh  surface  of  fracture,  with  no  bruises  by 
the  hammer.     It  is  often  well  to  leave  one  side  in  its  natural 
weathered  state,  to  show  the  eifects  of  weathering. 

Specimens  of  fossils  will,  of  course,  vary  in  size  with  the  nature 


404  APPENDIX. 

of  the  fossil.  When  possible,  the  fossil  should  "be  separated  from 
the  rock ;  but  this  must  be  done  with  precaution,  lest  it  be  broken 
in  the  process ;  it  should  not  be  attempted  unless  the  chances  are 
strongly  in  favor  of  securing  the  specimen  entire.  The  skilful  use 
of  a  small  chisel  and  hammer  will  often  expose  to  view  nearly  all 
of  a  fossil  when  it  is  not  best  wholly  to  detach  it.  When  the 
fossils  in  a  limestone  are  silicined  (a  fact  easily  proved  by  their 
scratching  glass  readily  and  their  undergoing  no  change  in  heated 
ucid),  they  may  be  cleaned  by  putting  them  into  an  acid,  and  also 
applying  heat  very  gently,  if  effervescence  does  not  take  place 
without  it.  The  best  acid  is  chlorohydric  (muriatic)  diluted  one 
half  with  water. 

Collections  both  of  rocks  and  fossils  should  always  be  made  from 
rocks  in  place,  and  not  from  stray  bowlders  of  uncertain  origin. 

3.  Packing.  —  For  packing,  each  specimen  should  be  enveloped 
separately  in  two  or  three  thicknesses  of  strong  wrapping-paper. 
This  is  best  done  by  cutting  the  paper  of  such  a  size  that  when 
folded  around  the  specimen  the  ends  will  project  two  inches  (more 
or  less,  according  to  the  size  of  the  specimen) ;  after  folding  the 
paper  around  it,  turn  in  the  projecting  ends  (as  the  end  of  the  finger 
of  a  glove  may  be  turned  in),  and  the  envelope  will  need  no  other 
securing.     Pack  in  a  strong  box,  pressing  each  specimen,  after  thus 
enveloping  it,  firmly  into  its  place,  crowding  wads  of  paper  between 
them  wherever  possible,  and  make  the  box  absolutely  full  to  the 
very  top  (by  packing-material  if  the  specimens  do  not  suffice),  so 
that  no  amount  of  rough  usage  by  wagon  or  cars  on  a  journey  of  a 
thousand  miles  would  cause  the  least  movement  inside. 

4.  Labelling.  —  A  label  should  be  put  inside  of  each  envelope, 
separated  from  the  specimen  by  a  thickness  or  more  of  the  paper. 
The  label  should  give  the  precise  locality  of  the  specimen,  and  the 
particular  stratum  from  which  taken,  if  there  is  a  series  of  strata  at 
the  place ;  it  should  also  have  a  number  on  it  corresponding  to  a 
number  in  a  note-book,  where  fuller  notes  of  each  are  kept,  together 
with  the  details  of  stratification,  strike,  and  dip,  sections,  plans, 
changes  or  variations  in  the  rocks,  and  all  geological  observations 
that  may  be  made  in  the  region.     A  specimen  of  rock  or  fossil  of 
unknown  or  uncertain  locality  is  of  very  little  value. 


APPENDIX. 


405 


D.  — List  of  Minerals  and  Rocks. 

The  minerals  and  rocks  enumerated  below  are  those  of 
highest  importance  to  the  geological  student.  The  list  of 
minerals  includes  100  specimens ;  that  of  rocks,  70.  Good 
collections  containing  the  170  specimens  numbered  as  be- 
low and  labeled  can  be  purchased  for  twenty  to  twenty-five 
dollars ;  and  all  schools  and  academies  in  which  the  subject 
is  taught  should  be  provided  with  one.  The  order  in  the  fol- 
lowing list  of  minerals  is  that  of  the  author's  small  Manual 
of  Mineralogy. 


Minerals. 


1.  Native  Sulphur. 

2.  Graphite. 

3.  Native  Copper. 

4.  Ckalcopyrite  (Copper  pyrites). 

5.  Malachite  (Copper  carbonate). 

6.  Galeuite      (Lead     sulphide)  ;     a, 

coarsely  crystallized  ;  b,  fine 
granular. 

7.  Sphalerite     (Zinc      blende)  ;     a, 

brown  or  yellow  ;  b,  black. 

8.  Calamine  (Zinc  silicate). 

9.  Cassiterite  (Tin  ore). 

10.  Pyrite  (Iron  disulphide)  :  a,  cubes ; 
b,  massive ;  c,  decomposing  and 
having  a  copperas-like  taste. 

11    Pyrrhotite  (Iron  sulphide). 

12.  Hematite  (Iron  sesquioxide)  :    a, 

ciystallized  ;  b,  massive  ;  c, 
earthy  red  oxide  or  ochre. 

13.  Magnetite  (Magnetic  iron  ore)  :  a, 

octahedral  crystals  ;  b,  granular 
massive. 

14.  Limonite    (Hydrous     iron-sesqui- 

oxide,  Brown  hematite)  :  a, 
botryoidal  or  stalactitic ;  b, 
earthy  or  yellow  ochre ;  c,  bog 
iron  ore. 

15.  Siderite  (Iron  carbonate) :  a,  light 

gray  ;  b,  dark  brown  from  par- 
tial alteration  toward  limonite. 

16  Manganese   oxide,  either  Pyrolu- 

site  or  Psilomelane. 

17  Corundum  (Alumina,  A12  03). 

li  Fluorite  (Fluor  Spar,  Calcium  flu- 
oride) :  at  crystal ;  b,  massive. 


18.  Gypsum    (Hydrous    calcium   sul- 

phate) :  a,  selenite  ;  b,  massive 
earthy. 

19.  Apatite  (Calcium  phosphate). 

20.  Guano  :  a,  b,  two  varieties. 

21.  Calcite   (Calcium   carbonate) :    a, 

cleavage  rhombohedron  ;  b, 
crystalline  ;  c,  travertine  j  d, 
stalactite  ;  e,  stalagmite. 

22.  Dolomite  (Magnesian  calcium  car- 

bonate). 

23.  Barite  (Barium  sulphate). 

24.  Quartz  :  a,  crystals ;  b,  group  of 

crystals  or  drusy  quartz  ;  c, 
massive  glassy  ;  d,  smoky ;  e, 
opaque,  pebbles,  /,  flint,  horn- 
stone,  or  chert ;  g,  jasper  ;  h, 
chalcedony. 

25.  Opal  :  a,  common  ;  b,  infusorial 

earth  (Diatom  earth,  electro- 
silicon  of  the  shops). 

26.  Pyroxene  :    a,  black  or  greenish- 

black  crystals  in  a  volcanic 
rock  ;  b,  green  pyroxene. 

27.  Amphibole  :     a,    b,    hornblende, 

black,  and  greenish-black  ;    c, 

actinolite,  green  ;  d,  treinolite, 

white  ;  e,  asbestus. 
Beryl. 
Chrysolite. 
Garnet  :  a,  dodecahedral  crystal  ; 

b,  trapezohedral  or  dodecahed'vl 

crystals  in  the  rock. 

31.  Zircon  :  2  crystals. 

32.  Epidote. 


406 


APPENDIX. 


33,  34.  The   Micas.  —  33,  Muscovite  : 

a,  b,  two  varieties  ;  34,  Biotite. 
35.  Scapolite. 

36-39.  The  Feldspars.  —  36,  Labra- 
dorite  ;  37.  Oligoclase  ;  38,  Al- 
bite  ;  39,  Orthoclase;  a,  white; 

b,  flesh-colored. 

40.  Chondrodite. 

41.  Tourmaline  :  a,  black  crystal ;  b, 

specimen  in  the  rock. 

42.  Andalusite :  chiastolite  in  slate. 

43.  Cyanite. 

44.  Staurolite  :  2  specimens. 


45.  Talc  :  a,  foliated  ;  b,  steatite  (soap- 

stone). 

46.  Glauconite  (Green  earth). 

47.  Serpentine  :    a,   light   green  ;    b, 

48.  Kaolinite  (Kaolin). 

49.  Chlorite  :  massive  granular. 

50.  Bitumen. 

51.  Mineral   coal  :    a,   anthracite  ;   I, 

bituminous  coal ;  c,  cannel  cod  ; 
d,  brown  coal  ;  e,  lignite. 

52.  Peat  :  a,  imperfectly  changed  ;  b, 

good  peat  ;  c,  muck. 


Rocks. 


1.  Fmgmental  non-calcareous. 

I.  Sand  :    a,  ordinary  of  seashore  ;  b, 

magnetic  iron  sand  with  gar- 
net sand,  from  seashore. 

2.  Clay  :     a,      common     brick-clay 

(burns  red)  ;  b,  Fire-brick  or 
Potters'  clay  (burns  white). 

3.  Sandstone  :  a,  white  or  grayish  ; 

b,  red  ;  c,  brown  ;  d,   granitic  ; 
e,  laminated  argillaceous  (flag- 
ging stone)  ;  f,  micaceous. 

4.  Conglomerate  :    a,    ordinary  ;     b, 

grit  ;  c,  calcareous. 

5.  Shale  :  a,  gray  or  reddish  ;  b,  car- 

bonaceous (black). 

6.  Tufa  (volcanic  sandstone  or  con- 

glomerate). 

2.  Metamorphic  Rocks. 

7.  Granite  :  a,  light  gray  ;    b,  flesh- 

colored,  not  coarse  ;  c,  coarse 
vein  granite  ;  d,  porphyritic  ;  e, 
a  granite  with  outer  part  rusted 
from  partial  decomposition. 

8.  Gneiss  :  a,  b,  two  varieties. 

9.  Mica  schist  :    a,  b,  two  varieties  ; 

c,  garnetiferous. 

10.  Hydromica  schist  :  a,  b,  ordinary 
varieties. 

II.  Chlorite  schist. 

12.  Argillite  (Roofing  slate)  :  a,  dark 

gray  or  blackish  ;  b,  red. 

13.  Syenyte  or  Quartz-Syenyte. 

14.  Syenyte-gneiss  (Hornblende 

gneiss). 

15.  Hornblende  schist. 

16.  Dioryte. 

17.  Labradioryte. 

18.  Quartzyte. 

19.  Buhxstone. 


3.   Calcareous  Rocks. 

Limestone  ;  A,  Uncrystalline  :  a, 
common  (better  if  fossiliferous)  ; 
b,  black  ;  c,  light  colored  ;  d, 
hydraulic ;  e,  chalk  ;  /,  shell 
limestone  (from  St.  Augustine, 
Florida) ;  B,  Crystalline  or  meta- 
morphic :  White  marble ;  g, 
gray  or  clouded  ;  li,  reddish  or 
brownish,  (partially  metamor- 
phic  of  Tennessee,  which  con- 
tains fossil  corals  of  the  Chajtetes 
group). 

Dolomite  (Magnesian  limestone)  ; 
a,  uncrystalline  ;  b,  crystalline, 
white  marble. 

Verd-antique  marble. 

4.  Igneous  Rocks. 

Doleryte  :  a,  compact  from  East- 
ern America  Triassic  areas  (Dia- 
base) ;  b,  same,  hydrous  or  chlo- 
ritic  ;  c,  amygdaloidal ;  d,  from 
modern  eruptions  ;  e,  dolerytic, 
or  ordinary  lava  ;  /,  scoriaceovis. 

Peridotyte  (Chrysolitic  doleryte, 
Basalt). 

Trachyte  :  a,  ordinary  ;  b,  pum- 
ice. 

Felsyte  :  a,  light  gray  or  whitish  ; 
a,  red  porphyry. 

Pitchstone  or  Pearlstone. 

Obsidian. 


Concretions:  a,  b,  c,  claystones,  one 

of  them  spherical  ;  d,  oolyte. 
Geode  :  2  specimens. 
Silicified  wood  :  2  specimens. 
Silicified  fossils  in  limestone. 


INDEX. 


NOTE.  —The  asterisk  after  the  number  of  a  page  indicates  that  the  subject  referred  to  is 
Illustrated  by  a  figure. 


Acadian  group,  206. 
Acalephs,  183,*  184. 
Acanthoteuthis,  298.* 
Acephals,  182* 
Acrodus  minimus,  178.* 

nobilis,  178. x 
Acrogens,  188. 

Carboniferous,  251. 

Devonian,  232, 
Actinia,  183.* 
Actinocrinus      proboscidialis, 

255* 

JSpyornis,  extinction  of,  373. 
Ages  in  Geology,  190,  Ul. 
Alabama  period,  331,  332. 
A:bite,  22. 
Algae,  187. 

Alleghany  coal-area,  241. 
Alluvial  deposits,  99,  356. 
Alps,  glaciers  in,  121. 
Alum,  83. 

Ambonychia  bellistriata,  214.* 
America,  North,  Geography  of, 

See  GEOGRAPHY. 
Ammonites,  293.* 

Humphrey sianus,  206.* 

Jason,  296.* 

placenta,  317.* 

tornatus,  297  * 

of  Mesozoic,  326. 
Amphibians,  176,  291,*  300.* 
Amphigenyte,  38. 
Amphipods,  180.* 
Amphitherium,  305.* 
Amygdaloid,  143. 
Anatifa,  180.* 
Anchitheriuui,341.* 
Anchura  Americana,  64.* 
Andalusite,  24.  * 
Angiosperms,  189. 

Cretaceous,  312,  313.* 

Tertiary,  334,  335.* 
Animal  kingdom,  173, 174. 
Anisopus,  tracks  of,  292.* 
Anogens,  186. 
Ant-eaters,  344. 
Anthracite,  25,  247- 

basin,  Penn.  160.* 
Anthracite,  origin  of,  146,  281 

vegetable  tissues  in,  260.* 
Anticline,  55  *  66. 
Apiocrinus,  65.* 


Appalachian  revolution,  277. 
Appalachians,    formation     of, 
164,  165,  168,  277,  378. 

folded  rocks  of,  279.* 

thickness    of    formations 

of,  230,  277. 
Araucariae,  189*. 
Archjean  time,  191, 199. 

N.  America,  199.* 
Archseoniscus  Brodiei,299.* 
Archaeopteryx,  304.* 
Archimedes  reversa,  255.* 
Arctic  coal-area,  243. 
Arenicola  piscatorum,  180.* 
Argillyte,  36. 
Artesian  wells,  105.* 
Arthrolycosa,  256  * 
Articulates,  175,  179, 180.* 
Asaphus  gigas,  214.* 
Ascidians,  180. 
Astarte  Conradi,  336.* 
Athyris  conceutrica,  63.* 

subtilita,  255.* 
Atmosphere,  agency  of,  86. 
Atolls,  78.* 
Atrypa,  63,*  236.* 
Auk,  extinction  of,  373. 
Aulopora  cornuta,  235.* 
Australia,  basaltic  columns  of, 
145.* 

Marsupials  of,  in  Quater- 
nary, 366. 
Azoic.    See  ARCH.EAN. 

Bacilaria  paradoxa,  187.* 
Baculites  ovatus,  317.* 
Bagshot  beds,  334. 
Bala  formation,  212. 
Barnacles,  180.* 
Basalt,  38. 

Basaltic  columns,  48,*  145.* 
Bathygnathus  borealis,  292.* 
Beach  formations,  44,  45,* 

112,113     ' 
Bear,  cave,  363. 
Beetles,  256. 

Belemnitella  mucronata,  317.* 
Belemnites,  297,  298,*,317.* 
Belodon  priscus,  292.* 
Bembridge  beds,  334. 
Bernese  Alps,  117. 
Bilin,  infusorial  bed  of,  336. 


Biotite,  23. 
Birds,  176. 

Cretaceous,  320,*  321  .* 

of      Connecticut    Valley. 
293.* 

of  Solenhofen,  304,*  327. 

Tertiary,  338. 
Birdseye  limestone,  211. 
Bituminous  coal,  25,  146,  247. 
Black  River  limestone,  211. 
Black  slate  of  Devonian ,  230. 
Bog  ore,  86. 
Bore,  109. 

Bowlders,  94, 119,  348,  341 
Bracluopods,  63  *  181,*    182, 
214  *  222,*  224,*  23o,* 
255,*  275. 

Brandon  fossil  fruits,  335.* 
Breccia,  34 
Brontotherium,  343. 
Brown  coal,  26,  311  332. 
Bryozoans,  181,*  183 
Buhrstone,  Tertiary,  333. 
Bulla  speciosa,  64.* 
Bunter  Sandstein,287. 
Buprestis,  299.* 

Calamites,  188,  233,  251,*  253, 

275. 

in  Triassic,  288 
Calamopsis  Danae,  335.* 
Calaveras  skull,  370. 
Calcareous  rocks,  31,  36. 
Calciferous  sand-rock,  211. 
Calcite,  27.* 
Callista  Sayana,  337-* 
Callocystites  Jewettii  183.* 
Calymene  Blumenbachii,  180.* 

215. 

Cambrian,  207. 

Camel,  Tertiary  American  342. 
Canadian  period,  210. 
Cancer,  180.* 
Canons,  94,  95.* 
Caradoc  sandstone,  212. 
Carbon,  25. 
Carbonates,  27,*  29. 
Carbonic  acid,  26,  83. 
Carboniferous  age,  240. 
Carcharodon  angiistidens, 

178  *  337,  338.* 
inegalodou,  837. 


408 


INDEX. 


Cardita  planicosta.  336  * 

Coelenterates,  175. 

Decapods,  179,  180.* 

Caryocrinus  oruatus,  222.* 

Coin-conglomerate,  370.* 

Delta,  of  Mississippi,  101.* 

Cascades,  94. 

Colorado,  canon  of,  40,  95.* 

Deltas,  100. 

Catopterus  gracilis,  291.* 
Catskill  period.  231. 

Columnaria  alveolata,  213. 
Comatulids,  184. 

Dendrophyllia,  183.* 
Denudation,  57,*  91. 

Cauda-galli  grit,  229. 

Comprehensive  types,  383. 

Desmids,  187,  234.* 

Cave  animals  of  Quaternary. 

Concretions,  47,*  48.* 

Detritus,  94. 

363. 

Conformable  strata,  57.* 

Devonian  age,  229. 

Cenozoic  time,  329. 

Conglomerate,  34. 

hornstone,  microscopic  or« 

general  observations    on, 

Conifers,  188,*  189,  233,  253. 

ganisms  in,  234.  * 

373. 

Connecticut  River  sandstone 

Diabase,  38. 

Cephalaspis,  238.* 

and  footprints,  285. 

Diamond,  25. 

Cephalates,  181.* 

terraces,  357.* 

Diatoms,  67,  68,*  187,*  335  * 

Cephalizatiou,  progress  in,  388. 

trap  rocks,  286. 

in  hornstone,  234.* 

Cephalopods,  181.* 

.Continents,    basin  -like   shape 

deposits  of,  312. 

of  Mesozoic,  326. 

of,  14.* 

Tertiary,  335.* 

Cestracionts,  178,*  179,   239, 

origin  of,  163. 

Dikes,  43,*  143,  286. 

299. 
Chsetetes     lycoperdon,     213, 

Contraction  a  cause  of  change 
of  level,  156. 

Dicotyledons,  188. 
Dinoceras,  341.* 

214.* 

Coprolites,  68,  303. 

Dinornis,  extinction  of,   372, 

Chain  -coral,  222,*  223. 

Coral  islands,  78,*  170. 

Dinosaurs,  302,  338. 

Chalcedony,  20. 

reef    of    the    Devonian, 

Dinothere,  3i3.* 

Chalk,  31,36,211,323. 

229. 

Dioryte,  36,  37. 

Champlain  period,  348,  355. 

reefs,  74,  77.* 

Dip,  52,  53.* 

Chazy  limestone,  211. 

Corals,  formation  of,  64,*  184. 

Diprotodon,  366. 

Cheirolepis  Traillii,  177.* 

recent,  183.* 

Dipterus.  238.* 

Cheirofheriuni,  300.* 

Coralline  crag,  334. 

Discina,  218,  382. 

Chenmng  period,  230. 

Corallines,  66,  187. 

Dislocated  strata,  52. 

Chlorite.  23. 

Corniferous  limestone,  229. 

Dodo,  extinction  of,  371,  372.* 

Chlorite  schist,  35 

period,  229. 

Doleryte,  38,  39,  M3. 

Chonete?  mesoloba  255.* 

Cornwall  lode,  43.* 

Dolomite,  27. 

setigera,  236.* 

Crabs,  179,  180.* 

Drift,  348. 

Chrysolite.  38. 

Crassatcllaalta.336.* 

sand-beds,  45,*  88. 

Cidaris  Blumenbachii,  294.* 

Craters,  130. 

scratches,  88,  349,  350.* 

Cinders,  131. 

Crepidula  costata,  337.* 

Dripstone,  37 

Cinuamomum,  Tertiary,  335.* 
Circumdenudation,  94. 

Cretaceous  period,  285,  310. 
America,  map  of,  320. 

Dromatherium  sylvestre,294.* 
Dudley  limestone,  221. 

Clathropteris.  289.* 

Crevasses,  117. 

Dunes,  88. 

Clay,  33. 

Crinoidal   limestone,   Subcar- 

Dykes.    See  DIKES. 

Clay-slate,  slate,  36. 

boniferous,  245. 

Dynamical  Geology,  62. 

Cleavage,  slaty,  49,  50,*  169. 

Crinoids,  65  *  183,*  184. 

Cliff-limestone,  230- 

Jurassic,  294.* 

Climate,  cause  of  changes  in, 

Primordial,  208. 

Eagre,  109. 

124. 

Silurian,  208,  214  *  222* 

Earth,  size  and  features  of,  6. 

Carboniferous,  262. 

223. 

relation  to  Man,  394. 

Cretaceous,  323. 

Subcarboniferous.       254, 

features,  origin  of,  156. 

Jurassic,  309. 

255.* 

interior  of,  161- 

Paleozoic,  273. 

Crocodiles,  319. 

Earthquakes,   origin   of,   102, 

Quaternary,  367. 

Crustaceans,  179,  180.* 

138,157. 

Tertiary,  347. 

Cryptogams,  186,  187. 

Ebb-and-flow  structure,  45.* 

Clinometer,  53  * 

Crystalline  rocks,  29. 

Echini,  183.* 

Clinton  group,  219. 

Crystallization.      See    META- 

Mesozoic,  294.* 

Coal,  kinds  of,  25. 

MORPHISM. 

Echinoderms,  183.* 

formation  of,  259. 
deprived  of  bitumen,  281. 
Coal-areas  of  Britain  and  Eu- 

Ctenacanthus major,  257.* 
Ctenoids,  176,  177.* 
Currents,  oceanic,  108,  110. 

Edentates,  Quaternary,  365.* 
Edestosaurus,  318.* 
Elephants,   Quaternary,    364, 

rope,  244.* 

Cyanitc,  24. 

365 

-  i  -areas  of  N.  America,  241, 

Cyathophylloid     corals,    185, 

Tertiary,  343 

242.* 

213,214,*222;*235.* 

Elephas      primigenius,      364, 

-beds,  characters  of  246 

Cyathophyllum         rugosum, 

369.* 

-beds,  formation  of,  261. 

235.* 

Elevation  of  coast  of  Sweden, 

-beds  of  Triassic,  290. 

Cycads.  189. 

362. 

-beds,  flexures  in,  278  * 

Triassic      and     Jurassic, 

of  Alps,  34G. 

-formation,  rocks  of,  245. 

288.* 

of  Green  Mountains,  216. 

-plantsofRichmond,289* 

Cycloids,  176,  177.* 

of  Himalayas,  346. 

290. 
-plants  of  the  Carbonifer- 

Cyclonema cancellata,  222  * 
Cyclopteris  linnseifolia,  289.* 

of  Rocky  Mountains,  345. 
of  Western  South   Amer- 

ous, 250.* 

Halliana,  232.* 

ica,  347. 

Coccoliths,  66.  187 

Cypris,  179. 

of  Quaternary,  348. 

Coccosteus,  237  * 

Cystideans,  183,*  223 

Elevations,  causes  of,  128,  156. 

Cockroaches,  256. 

Cythere  Americana,  180.* 

Emery,  21. 

INDEX. 


409 


Enaliosaurs,  258,*  300,*  301,* 

Freestone  of  Portland,  Ct.,  285. 

Gypsiferous  formation,  286. 

319. 

Fresh  waters,actiou  of,  90. 

Gypsum,  104,  220,  24!). 

Enorinus      liliifonnis,      183,* 

Fruits,  Carboniferous,  253  * 

Gyrodus  umbilicus,  177.* 

294.* 

Tertiary,  334,  335.* 

Endogens,  188,*  189. 

Fungi,  187. 

England,   geological   map   of, 

Fusuliua,  66.* 

:Ialy  sites  catenulata,  222.* 

244.* 

Fusus  Newberryi,  317.* 

Hamilton  period,  230. 

Entomostracans,  179,  180.* 
Eocene,  330. 

Harmony  iu  the  life  of  an  age, 
384. 

Eosaurus  Acadianus,  258.* 

Ganges,  detritus  of,  99. 

[lawaii,    volcanoes    or,    133,* 

Eoscorpius  carbonarius,  256.* 

Saugue,  42. 

136* 

Eozoou,  203.* 

Ganoids,  170,  177.* 

Heat,  124,  128. 

Ephemera,  291. 

Carboniferous,  257.* 

evidence  of  internal,  126. 

Eiiuiseta,  188,  233,  253. 
Equivalent  strata,  59. 

Devonian,  237.* 
Triassic,291.* 

Height    of  Aconcagua  peak, 
132. 

Erie  shale,  230. 

Garnet,  24.* 

of  Sorata,  132. 

Erosion  by  rivers,  90,  93,  102. 

Gasteropods,  64,*  181,*  182. 

of  Shasta,  132. 

glacial,  120. 

Geanticline,  56,  169. 

Hematite,  28. 

oceanic,  107.* 
Eruptions  of  volcanoes,  133. 

Genera,  long-lived,  275,  382. 
Genesee  shale,  230. 

Hempstead  beds,  334. 
tlerculaneum,  13i>. 

non-volcanic,  142. 

Genesis,  393. 

Elesperornis  regalis,  320.* 

Eschara,  181.* 

Geodc,  48.* 

Heterocercal,  177,*  238.* 

Estheria  ovata,  290.* 

Geography,  progress  in  North 

Hipparion,341.* 

Estuary  formations,  100. 

America,  163,  203,  204, 

Hitchcock,  »E.,    tracks     de- 

Euplcctella speciosa,  314.* 

272,  376. 

scribed  bv,  292.* 

Eurypterus  remipes,  224.* 

American,    in   Archaean, 

Holoptychius,  238.* 

Exogens,  188.* 

199  *  203,  269. 

Ilomalonotus,  222.* 

Exogyra  costata,  316.* 

in  Carboniferous,  263. 

Ilomocercal,  177.* 

Extermination  of  species,  218, 

iu  Cretaceous,  320.* 

Hornblende,  23. 

273,  328,  371. 

in  Devonian,  239. 

Hornblende  rocks,  35,  37. 

methods  of,  385- 

in  Mesozoic,  324. 

Horn?tone,  229. 

in  Paleozoic,  269. 

microscopic    remains    in. 

Fa^us,  335  * 

in  Quaternary,  373. 

234.* 

Fan-palm,  334. 

in  Silurian,  215,  224. 

Horse,  fossil,  340,  341.* 

Fasciolaria  buccinoides,   64,* 

in  Tertiary,  344.* 

Hot  Springs,  140,  141.* 

317.* 

Triassic,  306. 

Hudson's  Bay,  164. 

Faults,  54,*  279  * 
Favosites  Goldfussi,  235.* 

Goosynclinc,  56,  165. 
Geysers,  140,  141.* 

.    idson  River  shale,  212. 
Hyaena,  species  of,  363. 

Niagarensis,  222.* 
Feldspar,  22,  37. 

Giant's  Causeway,  144. 
Gilbert  Islands,  79.* 

Hybodus,  species  of,  178.* 
Hydroid  Acalephs,  184.* 

Felsyte,  38. 

Glacial  period,  347,  348,  360. 

Ilydromica  schist,  35. 

Ferns,  187,  188. 

Glacier,  great,  of  Switzerland, 

Devonian,  232.* 

117.* 

Carboniferous,  251.* 
Fiords,  351. 

scratches,  350.* 
theory  of  the  drift,  351. 

Ice  of  lakes  and  rivers,  115, 
116. 

Fishes,  176.* 

Glaciers,  116. 

glacier,  115,  116,  347. 

Age  of,  229. 

Glen  Roy,  benches  of,  359. 

Icebergs,  115,  122,  3f>l. 

Carboniferous,  257.* 

Globigerina,  66,*  185,*  186. 

Ichthyornis  victor,  321.* 

Devonian,  237.* 

Glyptodon,  866.* 

Ichthyosaurus,  301.* 

Mesozoic,  209,*  318.* 

Gneiss,  35. 

Igneous    rocks,    31,  37,  130, 

Silurian,  224. 

Goniatites,  first  of,  235. 

145,*  171. 

Teliost,  317,  318.* 
Fish-spines,  239,*  257.* 

last  of,  in  Triassic,  293. 
Marcellensis,  236.* 

ejections  of  Lake  Superior 
region,  216. 

Flags,  33,  44. 

Gorgonia,  183.* 

ejections,  Triassic,  286. 

Flint,  20,  312. 

Grammysia  bisulcata,  236  * 

lguanodon,302,  319. 

Flint  arrow-heads,  368. 

Granite,  35,  38. 

Infusorial  beds,  Tertiary,  336. 

Flow-and-plunge      structure, 

Graphite,  25,  69,  146,  200,202. 

Ink-bag,  fossil,  298* 

45,*  114. 

Graptolites,  213.* 

Inocerarnus       problematicus. 

Fluvio-marine  formations,  111. 

Greenland,  glaciers  of,  121. 

316,*  337. 

Folded  rocks,  55*  156,  200, 

changes  of  level  in,  362. 

Insects,  179. 

279.* 

Green  Mountains,  emergence 

first  of,  236. 

Footprints.    See  TRACKS. 

of,  216. 

Carboniferous,  256.* 

Foraminifera,  65,*  185.* 

limestone  of,  211. 

Devonian,  237.* 

Fossilization,  70. 

Green-sand,  311. 

Jurassic,  299.* 

Fossils,  use  of,  in  determining 

Gryphsea,  295,*  316.* 

Triassic,  299.* 

the  equivalency  of  stra- 

Guadaloupe, human  skeleton 

Irish  Deer,  364. 

ta,  3,  60. 

of,  370.* 

Iron  ore,  Archaean  ,  200.* 

list  of  localities  of,  399. 

Gulf  of  Mexico,   progress  of, 

Iron  ores,  28,  85,  86. 

number  of  species  of,  228, 

345. 

Carboniferous,  246, 

383. 

Gulf  Stream,  72,  125. 

Isopods,  180.* 

Fragrnental  rocks,  29,  33. 

Gymnosperms,  189. 

Itacolumite,  36. 

410 


INDEX. 


Jasper,  20. 

Joint*  ia  rocks,  49,*  169. 

Jurassic  period,  285. 

Kaolin,  34,  84,  86. 
Kerosene,  248. 
Keuper,  287. 

Keweenaw  Point,  211,  216. 
Kilauea,  1§4. 
Kingsmill  Islands,  79.* 
Kirkdale  cavern,  363. 

Labradorite,  22,  38,  200. 

Labyrinthodouts,  257,*  300.* 

Laccoliths,  145. 

Lacustrine  deposits,  358. 

Lake    Champlain    in    Quater- 
nary, 358. 

Mempliremagog,        Devo- 
nian coral-reef  of,  230. 

Lakes,  origin    of  Great,   272, 
377. 

Lake-dwellings,  370. 

Lamellibranchs,  181,*  182. 

Laminated  structure,  32,  44, 
45.* 

Lamna  clegans,  178,*  338.* 

Lind-slides,  105. 

Lava,  38,  130, 143. 

Layer,  41. 

Lecanocrinus  elegans,  214.* 

Leguminosites,  313.* 

Leperditia  alta,  224.* 

Lepidodendra,  233. 

Lepidodendron        aculeatum, 

251.* 
priinaevum,  232.* 

Lepidosteus,  177.* 

Leptaena  sericea,  214.* 
transversalis,  222.* 

Leptaenas,  last  of,  295. 

Lesley,  results  of  denudation 
96.* 

Leucite,  38. 

Level,   change   of,    in   Green- 
land, 362. 

changes  of,  in  the  Quater- 
nary, 358,  360,  361. 
origin  of  changes  of.  106, 
128,  139,  156. 

Level.     See  ELEVATION. 

Lias,  287. 

Libellula,299.* 

Life,  agency  of,  in  rock-mak- 
ing, 62. 

distribution  of  marine,  70. 
general  laws  of  progress  of, 

protective  and  destructive 
effects  of,  80,  81. 

Life.     See  SPECIES. 

Lignite,  26,  311,  332,  347. 

Lignitic  period,  330,  332,  345. 

Limestone,  36,  37. 

formation  of,  63,  77,  86, 
269. 

Limestones  of  Mississippi  Val- 
ley, 267.* 

Limonite,  28,  85. 

Limulus,  179, 180. 


Lingulse,  68,  181,*  207,*  218, 

382. 

Lingula  nags,  207. 
Liriodendron  Meekii,  313* 
Lithostro  t  ion  (Juiiadense ,  255.  * 
Llandeilo  flags,  212. 
Llandovery  beds,  221. 
Localities  of  fossils,  list  of,  399. 
Locusts,  256. 
London  clay,  334. 
Lorraine  shale,  212. 
Lower  Ilelderberg,  220. 
Ludlow  group,  221. 
Lycopods,  188,223,232,*251  * 


Machaerodus,  364. 

Made,  24. 

Madagascar  JEpyornis  of,  373.  * 

Maguesiau  limestone,  27,  36, 

211. 

Magnetite,  29. 
Magnolia,  334. 
Mammals,  176. 

Age  of,  330. 

first  of,  294.* 

Jurassic,  305  * 

Tertiary,  3i9,  338.* 

Triassic,  294,*  305. 
Mammoth  Cave,  103.* 
Man,  Age  of,  329,  347,  368. 

fossil,     of      Guadaloupe. 
370.* 

the  head  of  the  system  of 

life,  371,  387. 

Tlap  of  Pennsylvania  coal  re- 
gion, 242.* 

of  England,  244.* 

of  Ilawaian  Is.,  17  *  133  * 
136.* 

of  Mammoth  Cave,  103.* 

of  vicinity  of  Naples,  398.* 

of  N.  Jersey  Coast,  12.* 

of  N.  America,  Archaean, 
199.* 

of  N.    America,   Cretace- 
ous, 320.* 

of  N.  America,  Tertiary, 
344.* 

of  New  York  and  Canada, 
197.* 

of  Ocean,  11.* 

of  United  States,  195.* 

of  World,  8* 
Marble,  37. 

of  Green  Mountains,  211, 

217. 

Marcellus  shale,  230. 
Margarita  Nebrascensis,  64.* 
Marine  formations,  112. 
Marl,  76,  311. 
Marsupials,  176,  366. 

Triassic,  294,*  305.* 

Jurassic,  305.* 

Massive  structure,  32,  44,  45.* 
Mastodon,  Quaternary,  364.* 

Tertiary,  343. 
Mastodonsaurus,  300.* 
Mauna.     Sec  MOUNT. 
May-flies,  256.* 
Medina  group,  219,  223. 


Medusae,  183,*  184. 
Megacerod  Hiberuicus,  364. 
Mega.lo.iaur,  302. 
Megatuere,  3u5.* 
MeUphyre,  38. 
Mer-dc-glace,  117. 
Mesozoic  time,  283. 

general  observations    on, 
324. 

geography  of,  324. 

life  of,  326. 

Metauiorpliic  rocks,  30,  35,  37. 

Mefcamorphism,    nature     and 

cause  of,  128,  145,  LJV, 

168. 

Miamia  Bronsoni,  256.* 
Mica,  22. 
Mica-schist,  35 
Michigan  coal -area,  241. 
Microdon  bellistriatus,  236.* 
Microiites,  39. 

Microscopic    organisms,    66,* 
67,*    68,*    187,     234,* 

235.* 

Millepores,  184. 
Mineral  coal.     See  COAL. 

oil,  26,  248. 
Miocene,  330. 

Mississippi  River,  amount  of 
water  of,  91. 

delta,  of,  101.* 

detritus  of,  99. 
Moa,  extinction  of,  372. 
Mollusks,  175,  180,  181.* 
Monadnock,349. 
Monocline,  56. 
Moraines,  119. 
Mosasaur,  318,*  319.* 
Mountains,    making   of,   159. 
163,  165,  216,  345. 

of  Paleozoic  origin,  271. 

made  after  the  close  of  tue 
Paleozoic,  277. 

made  after  the  Jurassic, 
309. 

made  during  the  Tertiary, 
344. 

See  ELEVATIONS. 
Mount  Blanc,  117. 

Holyoke,  144,  286. 

Loa,  133,*  136*  138. 

Tom,  144. 

Vesuvius,  130  *  138,  398. 
Muck,  76. 
Mud-cones,  142. 
Mud-cracks,  46. 
Muschelkalk,  287. 
Muscovite,  £3. 
Myriapods,  179,  256. 
Naples,  map  of  vicinity,  398.* 
Nautilus,  181,*  218,  382. 

in  the  Silurian,  215. 
Nautilus  tribe,  number  of  ex- 
tinct species  of,  383 
Neolithic  era,  369. 
N(Sv<§,  116. 

New  Brunswick  coal-area,  241. 
New  Caledonia  reefs,  80. 
New  South  Wales  cliff,  107.* 
Niagara  Falls,  rocks  of,  40,* 


INDEX. 


411 


Niagara  Falls  group,  219. 

River,  gorge  of,  <J4,  375. 
Noeggerathia.       See    CYCLOP- 

TEBIS. 

North  America,  form  of,  14. 
geography  of.     See  GEOG- 
RAPHY. 

Norwich  crag,  334. 
Notidauus  priinigenius,  178.* 
Nototherium,  366. 
Nova  Scotia  coal-area,  241. 
Nullipores,  66, 187. 
Nuummlltes,  66,*  333.* 
Nummulitic  limestone,  333. 
Nuts,  fossil,  251,*  253,  334.* 

Oak,  334. 

Obsidian,  39. 

Ocean,  depression  of,  9,  12.* 

effects  of,  106. 

Oceanic  basin,  6,11,*  70,  156. 
Ochre,  yellow,  28,  82. 
Ohio,   coral-reef   of  Falls  of, 

230. 

Oil,  mineral,  26,  248 
Old  red  sandstone,  231. 
Olivine,  38. 

Oiieida  conglomerate,  219. 
Onondaga  limestone,  229. 
Oolitic  structure,  47. 
Oolyte,  37,  287. 
Orbitolina  Texana,  315.* 
Oreodoa  gracilis,  343.* 
Orient,  charactcriotics  of,  6. 
Origin  of  species,  392. 
Oriskany  period,  205, 21U,  221. 
Orohippus,  340,  341.* 
Orthis  occidentals,  214.* 

testudiuaria,  214.* 

varica,  222  * 
Orthoceras  junceum,  214.* 

last  of,  296,  326. 
Orthoclase,  22. 

Osmeroides  Lewesiensis,  318.* 
Ostracoids,  180.* 

of  Triassic,  290- * 
Ostrea  sellseformis,  336.* 
Otozoum  Moodii,  292.* 
Outcrop,  52.* 
Ox,  first  of,  344. 
Oyster,  Tertiary,  337. 

Paleaster  Niagarensis,  183.* 
Palaeoniscus  lepidurus,  177.* 

Freieslebeni,  177,*  257.* 
Paleolithic  era,  368. 
Paleothere,  339. 
Paleozoic  time,  204. 

disturbances  closing,  276. 

general  observations    on, 

266. 

Palephemera  mediaeva,  291.* 
Palisades,  286. 
Palms,  first  of,  312. 

Tertiary,  335.* 
Palpi pes  priscus,  299.* 
Paludina  Fluviorum,  295.* 
Paradoxides  Harlani,  208  * 
Paris  basin,  Tertiary  animals 

of,  339. 
Paumotu  Archipelago,  79. 


Pearlstone,  39. 
Peat,  formation  of,  75. 
Peccary,  fossil,  342. 
Pecopteris         btuttgartensis. 

289.* 

Pemphix  Sueurii,  299.* 
Pentacrinus      Wyville-Thom- 

soni,  65.* 
Pentamerus  galeatus,  224.  * 

oblougus,  22^.* 
Pentremites,  254,  255.* 
Peridotyte,  38,  39. 
Permian  period,  241,  249. 
Petraia  corniculum,  214.* 
Petroleum,  248. 
Petrology,  19,  20. 
Phacops  bufo,  236.* 
Phascolotherium,  305.* 
Phenogams,  187,  188. 
Phyllyte,  36, 

Physiographic  Geology,  6. 
Pictured  rocks,  211. 
Pitchstone,  39. 
Plants,  67,  80, 173, 186. 

Carboniferous,  249,*  250.* 

Cretaceous,  312.* 

earliest  marine,  202,  207. 

Devonian,  232.* 

Silurian,  228. 

Tertiary,  335.* 

Triassic,  288,*  289. 
Platephemera  antiqua,  237.* 
Platyceras  augulatum,  222.* 
Plcsiosaurs,  301,*  302,  319. 
Plourotomaria  tabulata,  255.* 
Pliocene,  330. 
Pliosaur,  302. 
Plumbago,  25. 

Podozamites  lanceolatus,  289.* 
Polycystines,  186. 
Polyps,  184.* 
Polythalamia.      See   FORAMI- 

NIFERA. 

Pompeii,  139,  398. 
Porphyritic  rocks,  32,  38. 
Portland  (England)  dirt-bed, 

(Connecticut)     freestone, 

285. 

Potsdam  sandstone,  206. 
Primordial  period,  206. 
Prionastraea  oblonga,  294.* 
Productus  Nebrascensis,  255  * 
Protozoans,  175,  185,*  313. 
Pterichthys,  237.* 
Pterinea  emacerata,  222.* 
Pterodactyl,  303,*  319. 
Pterophyllum,  289.* 
Pteropods,  182.* 
Pterosaurs,  303,*  319, 
Ptilodictya,  214.* 
Pudding-stone,  34. 
Pumice,  39,  131 
Pupa  vetusta,  255.* 
Pyrifusus,  64,*  317.* 
Pyrite,  29,  82. 
Pyroxene,  23. 
Pyrrhotite,  29,  82. 

Quadrupeds.     See  MAMMALS. 
Quaquaversal  structure,  45.* 


Quartz,  20.* 

Quartz  rock,  or  Quartzyte,  36. 
Quaternary,  329,  347,  367. 
Quebec  group,  211. 
Quercus,  Tertiary,  335.* 

Radiates,  175,  183.* 
Radiolarians,  67,*  186.* 
Rain-prints,  47,*  306, 
Rauiceps  Lyellii,  258.' * 
Raphistoma  lenticularis,  214.  * 
Rays,  178. 

Reefs,  coral,  77,  78.*     ' 
Re-gelation,  119. 
Reindeer  era,  361,  368. 
Reptiles,  176 

Mesozoic,  291,  292  *  300  * 
318,*  328. 

Paleozoic,  258.* 
Reptilian  age,  284. 
Rhabdoliths,  66,  187. 
Rhinoceroses,  Tertiary,  342.* 

Quaternary,  364. 
Rhizopods,  65,*  67,*  185.* 

Cretaceous,  313, 

formation  of  deposits  by, 

65,  67 

Rhode  Island  coal-area,  241. 
Rhynchonella    pyramidatum, 

Rhynchotreta  cuneata,  222.* 
Rill-marks,  46  *  114. 
Ripple-marks,  46,*  114 
Rivers,  action  of,  90 

of  Paleozoic  origin,  272. 
River  terraces,  357,* 360* 
Roches  moutonne"es,  120, 121.* 
Rock,  definition  of,  19. 
Rocks,  constituents  of,  20. 

formation  of  sedimentary, 
90,  100,  111,  112,  122 

fragmented,  29. 

kinds  of,  29. 

metainorphic,  35,  145. 

of  Mississippi  Valley,  sec- 
tion of,  267.* 

origin  of  Archaean,  201. 

origin  of  Paleozoic,  268. 

thickness  of  Paleozoic  in 
North     America,     267, 

377. 

Rocky   Mountains,  origin  of, 
164,  170,  345. 

Mountain  coal-area,  382. 
Rotalia,  «6,*  186.* 

Sabal,  334. 

St.  Lawrence  River  in  the  Qua- 
ternary, 358. 

St.  Peter's  sandstone,  211. 
Saliferous    group    of    Britain 
and  Europe,  287. 

rocks  of  New  York,  220. 
Salina  rocks,  220,  226. 
Salisbury  Craigs,  144. 
Salix  Meekii,  313  * 
Salt,  28. 

of  coal  formation,  248. 

of  Salina,  etc.,  220. 

of  Triassic,  287. 
Sand,  33,  86. 


412 


INDEX. 


Sand-banks,  112. 
Sand-scratches,  88. 
Sandstone,  84,  36. 
Sapphire,  21. 

Sassafras  (Jretaceum,  313.* 
Sauropus  primsevus,  258.* 
Scaphites  larvaeformis,  817  * 
Schist,  schistose  rocks,  32,  35. 
Schoharie  grit,  229. 
Scolithus  linearis,  208. 
Scoria,  39, 131. 
Scorpions,  first  of,  256.* 
Sea-beaches  elevated,  358. 
Sea-weeds,  187. 

Section   of  New  York  rocks, 
198.* 

of  the  series  of  rocks,  193  * 
Sections    of    Paleozoic  rocks, 

231,*  267,*  2i~9.* 
Sedimentary  beds,   formation 

of,  SO,  100,  111,  112, 122. 
Selachians,  178.* 

Carboniferous,  256.* 

Devonian,  239,* 
Serolis,  180* 
Serpentine,  23. 
Shale,  32,  C3, 34,  44.* 
Sharks,  178,  256.* 

Devonian.  239.* 

Teeth,  178,*  299,  338.* 
Shasta,  height  of.  133. 
Siderite,  29,  85. 
SigillariaHallii,232.* 

Carboniferous,  252.* 
Silica,  or  Quartz,  20. 
Silicates,  20,  21. 
Siliceous  rocks,  32 

shells,  microscopic,  66, 
67,*  68,*  185*  180,* 
187,*  234,* 312,  335.* 

waters  of  Geysers,  142. 
Silt,  94,  99, 100. 
Silurian  age.  205. 

Upper,  219. 
Siphonia  lobata,  315.* 
Slate,  32,  33,  36- 
Slaty  cleavage,  32,  49,*  156, 

169, 

Sloths,   gigantic,  of    Quater- 
nary, 366.* 
Snakes,  first  of,  338. 
Soapstone,  23. 

Solenhofcn  lithographic  lime- 
stone. 287. 
Solfataras,  140. 
Solitaire,  372.* 
South  America,  form  of,  14. 

changes  of  level  in,  361. 
Spathic  iron,  29. 
Species ,  exterminations  of,  218, 


Sphagnous  mosses,  75. 
Sphenopteris      Gravenhorstii 

251.* 
Spicules  of  Sponges,  67,*  185, 

234,*  314.* 
Spiders,  179,  256.* 
Spinax  Blainvillii,  178.* 
Spirifer  cameratus,  255.* 
macropleurus,  224.* 
mucrouatus,  236.* 


Spirifer  striatus,  63.* 

Tracks  of  insects,  291.* 

Hcitcotti,  295.* 

of  reptiles,  Carboniferous, 

Spirilers,  last  of,  326. 

258.* 

sponges,  67*  185,  314.* 

of  reptiles,  Triassic,  292.  * 

Cretaceous,  315.* 

of  Trilobites,  208.* 

Sponge-opicules,  67.* 

Transportation  by  rivers,  98. 

in  hornstone,  234.* 

Trap,  38. 

Spores  in  coal,  259.* 

of    Connecticut     Valley, 

stalactites,  37. 

etc.,  286. 

Stalagmite,  37. 

columnar,  145.* 

Star-fishes,  184.* 

Travertine,  32,  37,  142. 

Statuary  marble,  37. 

Tree-ferns,  251. 

Staurolite,  25. 

Trenton  period,  210. 

Steatite,  23. 

Triassic  period,  285. 

Stictopora  acuta,  214.* 

Trigonia  clavellata,  295.* 

Stigmarise,  251,*  252. 
Strata,  definition  of,  39,  41. 

Trigonocarpus    tricuspidatus, 

251.* 

positions  of,  50,  51  *  53* 

Trilobites,    180,*    207,    208,* 

58. 

214,*  222,*  236*275. 

3traticulate  structure,  44. 

beginning  and  ending  of 

Stratification,  39,  40,*  44.* 

fnera,  273.* 

Strike,  54.* 

,131. 

Strophomena      rhomboidalis, 

Turrilitcs  catenatus,  317.* 

222. 

Turritella  carinata,.33G.* 

Subcarboniferous  period,  240, 

Turtles,  Cretaceous,  319. 

245- 

Jurassic,  303. 

'Submarine  eruptions,  139. 

Tertiary,  338. 

Subsidence  of  coast  of  New 

Jersey,  362. 
of  Greenland,  recent,  362. 
Subsidences  of    volcanic    re- 

Unconformable strata,  57.* 
Under  -clays,  246. 
Unstratified  condition,  41.* 

gions,  139. 
Subterranean  waters,  102. 
Sweden,  Quaternary  of,  359. 
changes  of  level  in,  362. 
Syenyte,  35,  37. 

Upper  Helderberg,  229. 
Upper  Silurian,  219. 
Ursus  spelseus,  363. 
Utica  shale,  211. 

Syncline,  56.* 
Synclinorc,  167. 
Syringopora  Maclurii,  235.* 
System,  definition  of,  41. 

Valleys,  formation  of,  91. 
Veins,  41,*  129,  150. 
Vertebrate-tailed  fiehes,  177,* 
238* 

Vertebrates,  175,  176. 

Talc,  23. 
Talcose  slate,  35. 

first  of,  224. 

T7V*oTiT7ino     1QA  =»';  1^?R    QQQ 

Tapirus  Indicus,  339.* 
Teliost  fishes,  176.* 
Cretaceous,  317,318,*328. 

Vesuvius,  J.oJ,"  100,0*70. 
Viviparus  fluviorum,  295.* 
Volcanoes,  130. 

Tertiary,  337. 
Tentaculites,  223,  224.* 
Terebratula,  63,*  181.* 

Waldheimia,  63.* 
Water,  action  of,  90. 

Terebratulina,  63.* 
Terraces  on  Connecticut  River, 

freezing  and  frozen,  115. 
Waves,  action  of,  107. 

357.* 
of  Scotland,  359. 
origin  of,  100,  355,  359. 

Wealden,  287. 
Wenlock  limestone,  221. 
Whales,  first  of,  338. 

Tertiary  age,  330. 
Tetradecapods,  179.* 

Winds,  effects  of,  86,  110. 
Wind-drift  structure,  45,*  88 

Tetragonolcpis,  299.* 

Woolwich  beds,  334. 

Thanct  sands,  334. 
Thecodonts,  259. 

Worms,  179,  180,*  208. 

Thrissops,  177.* 
Tidal  currents,  108. 
Tiger,  343. 

Xiphacantha,  186.* 
Xiphodon  gracile,  340  * 

Time,    length    of   geological, 

Yoldia  limatula,  337.* 

375. 
Time-ratios,  269,  324,  375. 

Yorktown  period,  331. 

Titanothere,  342.* 

Tourmaline,  24.* 

Zamia,189,288.* 

Trachyte,  38,  39,  14a 
Trachytic  hills,  138. 
Tracks  of  Birds,  203.* 

Zaphrentis  bilateralis,  222.* 
Rafinesquii,  235.* 
Zeacrinus  elegans,  256.* 

of^Cheirotherium,  300.* 

Zeuglodon,  340. 

of 


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